Advanced Fastly Interview Questions [2025]

Core Fastly Concepts

1. What is Fastly’s primary role in content delivery?

Fastly’s global CDN delivers low-latency content using over 100 points of presence in 90+ countries. It leverages edge caching, Anycast routing, and real-time analytics to optimize performance. CI/CD pipelines automate configurations, aligning with DevSecOps for scalable, secure delivery, ensuring high availability and enhanced user experiences globally.

2. How does Fastly’s Edge platform handle traffic spikes?

Fastly’s Edge platform manages traffic spikes with auto-scaling servers, Anycast routing, and edge caching to distribute load efficiently. Real-time logs monitor traffic patterns, while CI/CD automates rule updates. This DevSecOps-aligned approach ensures minimal latency, high availability, and secure performance during sudden demand surges in production.

3. When is Fastly’s VCL ideal for web applications?

Fastly’s VCL is ideal for web applications needing custom edge logic, like real-time content personalization or A/B testing, but less suited for simple static delivery. Logs track VCL performance, and CI/CD automates updates. DevSecOps alignment ensures secure, scalable configurations, supporting dynamic apps with reliable delivery.

4. Where are Fastly’s Edge servers located globally?

• Over 100 POPs across 90+ countries near ISPs.
• Peering points optimize low-latency routing.
• Logs capture deployment metrics for monitoring.
• CI/CD automates edge configuration updates.
• DevSecOps ensures secure, scalable deployments.
• Supports global high availability.
• Reduces latency for end users.

5. Who configures Fastly’s security policies?

Security engineers configure Next-Gen WAF rules, SREs monitor threats via logs, and DevOps automate updates with CI/CD. This collaborative DevSecOps approach ensures secure, scalable configurations. Real-time logging and auditing enable rapid threat response, maintaining robust protection for applications in production environments.

6. Which Fastly services enhance cloud security?

• Next-Gen WAF protects against app-layer attacks.
• Bot Management detects malicious bots with ML.
• DDoS Protection mitigates volumetric attacks.
• Logs track security events for analysis.
• Integrates with Sysdig for monitoring.
• DevSecOps ensures scalable security.
• Safeguards cloud applications effectively.

7. How does Fastly mitigate DDoS attacks?

Fastly mitigates DDoS attacks using real-time traffic scrubbing, rate limiting, and behavioral analysis to filter malicious traffic. Logs track attack patterns, and CI/CD automates rule updates. This DevSecOps-aligned strategy ensures resilient, scalable defense, maintaining application availability during attacks. Explore PagerDuty for incident response.

8. What is Fastly’s approach to Edge computing?

• Compute@Edge supports serverless Rust/JS/Go execution.
• Optimizes dynamic content at the edge.
• Logs execution metrics for performance monitoring.
• CI/CD automates code deployments.
• DevSecOps ensures secure, scalable execution.
• Reduces latency for real-time apps.
• Supports efficient DevOps workflows.

CDN and Performance Questions

9. How do you optimize Fastly CDN for video streaming?

Optimize video streaming with Fastly’s Media Shield, enabling adaptive bitrate switching and edge caching. Monitor performance via Control Center, log latency metrics, and automate updates with CI/CD. This DevSecOps-aligned approach ensures low-latency, scalable streaming, delivering seamless user experiences even during high-traffic scenarios.

10. Why do cache misses occur in Fastly CDN?

Cache misses occur due to short TTLs, misconfigured VCL rules, or uncacheable content. Validate headers in Control Center, log misses for analysis, and test caching with simulated traffic. CI/CD automates updates, aligning with DevSecOps to optimize cache hit ratios and enhance content delivery performance.

11. What is Fastly’s Dynamic Content Acceleration?

Dynamic Content Acceleration optimizes dynamic content delivery using VCL for custom logic and Anycast routing for efficiency. Logs track performance, while CI/CD automates updates. This DevSecOps-aligned solution reduces latency for dynamic web applications, ensuring reliable, scalable delivery under high traffic in production environments.

12. How do you purge Fastly’s CDN cache?

• Use Fastly API for URL or tag-based cache invalidation.
• Log purge events for audit trails.
• Automate purges via CI/CD pipelines.
• Test with simulated content updates.
• Align with DevSecOps for secure operations.
• Ensure instant fresh content delivery.
• Monitor purges in Control Center.

13. Where do you monitor Fastly CDN performance?

Monitor CDN performance in Fastly Control Center, Prometheus for metrics, and Grafana for visualization. Log cache hits and latency, while CI/CD validates monitoring configs. This DevSecOps-aligned setup ensures observability, enabling rapid issue detection and resolution for reliable performance in production environments.

14. Who optimizes Fastly CDN rules?

DevOps engineers optimize VCL rules for performance, SREs monitor latency and cache metrics, and security teams ensure compliance. Logs track changes, and CI/CD automates updates. This DevSecOps-aligned collaboration ensures efficient, secure CDN configurations, enhancing content delivery performance for global applications.

15. Which settings reduce latency in Fastly CDN?

• Enable Dynamic Content Acceleration for routing.
• Set long TTLs for cacheable content.
• Use Anycast for efficient traffic routing.
• Log latency metrics for analysis.
• CI/CD validates rule updates.
• Align with Spacelift CI/CD.
• Ensure low-latency global delivery.

Discover Spacelift automation for CDN optimization.

DNS Management Questions

16. How do you configure Fastly’s Edge DNS for fast resolution?

Configure Edge DNS with Anycast routing for proximity-based resolution and DNSSEC for security. Log query performance, automate updates via CI/CD, and test with dig. This DevSecOps-aligned approach ensures low-latency, secure DNS resolution, supporting high-availability applications with reliable configurations.

17. How do you set up DNS failover for critical apps?

• Create failover policies with health checks.
• Assign backup origins for redundancy.
• Log failover events for analysis.
• CI/CD automates DNS config testing.
• Test failover with API simulations.
• Align with DevSecOps for reliability.
• Ensure uninterrupted app availability.

18. Why does DNS resolution fail in Fastly?

DNS resolution fails due to misconfigured records, propagation delays, or incorrect TTLs. Validate records with dig, log errors, and test zones via API. CI/CD automates updates to prevent issues, aligning with DevSecOps to ensure reliable, secure DNS resolution for critical applications in production.

19. Where do you manage Fastly DNS records?

Manage DNS records in Fastly Control Center or via API for automation. Log changes for auditing, validate with CI/CD, and test configurations. This DevSecOps-aligned approach ensures secure, scalable DNS management, enabling rapid updates and reliable resolution for global applications.

20. Who handles DNS updates in Fastly?

• Network engineers update zones via Control Center.
• DevOps automate updates with API integrations.
• Security teams ensure DNSSEC compliance.
• Logs track changes for audit trails.
• CI/CD validates updates for accuracy.
• DevSecOps ensures secure updates.
• Minimizes downtime during changes.

21. Which DNS records are critical for Fastly?

• A/AAAA for IP resolution.
• CNAME for edge server aliasing.
• MX for mail server routing.
• TXT for SPF/DKIM authentication.
• Log changes for real-time analysis.
• Align with Sysdig monitoring.
• Ensure secure DNS configurations.

22. How do you troubleshoot DNS propagation issues?

Troubleshoot DNS propagation by validating records with dig, checking TTLs, and logging delays. Use Edge DNS for faster resolution, automate updates via CI/CD, and test with API simulations. This DevSecOps-aligned approach minimizes downtime, ensuring reliable DNS performance. Explore Sysdig for monitoring.

DDoS Mitigation Questions

23. How does Fastly handle DDoS attacks?

Fastly mitigates DDoS attacks with real-time traffic scrubbing, rate limiting, and behavioral analysis. Logs track attack patterns, while CI/CD automates rule updates. This DevSecOps-aligned approach ensures resilient defense, maintaining application availability during volumetric or app-layer attacks in production environments.

24. How do you configure rate limiting for DDoS mitigation?

• Set request thresholds in Control Center.
• Define per-IP rate limits for flood control.
• Log rate limit events for analysis.
• CI/CD automates rule testing.
• Test with simulated traffic loads.
• Align with DevSecOps for security.
• Block volumetric DDoS attacks.

25. Why is Fastly’s DDoS Protection critical?

Fastly’s DDoS Protection uses distributed scrubbing and rate limiting to filter malicious traffic, ensuring app availability. Logs monitor attack patterns, and CI/CD automates updates. This DevSecOps-aligned solution provides scalable, resilient defense, protecting critical applications from disruption during DDoS attacks in production.

26. What happens during a DDoS attack on Fastly?

During a DDoS attack, Fastly diverts traffic to scrubbing centers, applies WAF rules, and enforces rate limiting. Logs analyze patterns, while CI/CD updates defenses dynamically. This DevSecOps-aligned approach ensures rapid mitigation, minimizing downtime and maintaining application availability under high-volume malicious traffic.

27. How do you monitor DDoS attacks in Fastly?

• Use Fastly analytics for attack insights.
• Integrate Prometheus for real-time metrics.
• Log attack events for debugging.
• CI/CD configures automated alerts.
• Visualize with Grafana dashboards.
• Align with DevSecOps for monitoring.
• Detect and respond to attacks swiftly.

28. Where do you configure Fastly’s DDoS protection?

Configure DDoS protection in Fastly Control Center with rate limiting and scrubbing rules. Log traffic patterns, validate configs with CI/CD, and test with simulated attacks. This DevSecOps-aligned setup ensures scalable protection, enabling rapid threat detection and response while maintaining application uptime.

29. Which WAF settings optimize DDoS mitigation?

• Enable managed rules for common threats.
• Configure custom rules for specific attacks.
• Log WAF events for real-time analysis.
• CI/CD automates rule updates.
• Test with simulated attack traffic.
• Align with DevSecOps for security.
• Protect against app-layer DDoS.

Learn about Spacelift automation for WAF configs.

Cloud Security Questions

30. How do you configure Fastly’s Next-Gen WAF?

Configure Next-Gen WAF with managed rules for common threats and custom rules for specific vulnerabilities. Log threat events, automate updates via CI/CD, and test with simulated attacks. This DevSecOps-aligned approach ensures robust cloud security, protecting applications from sophisticated attacks while maintaining performance.

31. How do you set up Fastly’s Bot Management?

• Define bot detection rules in Control Center.
• Use ML-based behavioral analysis.
• Log bot activity for auditing.
• CI/CD automates rule updates.
• Test with simulated bot traffic.
• Align with DevSecOps for security.
• Block malicious bots effectively.

32. Why does a WAF rule block legitimate traffic?

WAF rules block legitimate traffic due to overly broad expressions or false positives. Review rules in Control Center, whitelist trusted IPs, and log blocked requests. CI/CD automates testing, aligning with DevSecOps to ensure accurate detection, minimizing disruptions, and maintaining reliable application access.

33. How do you implement Fastly’s Zero Trust model?

Implement Zero Trust with Fastly Access for identity-based authentication and Gateway for traffic filtering. Log access events, automate policies via CI/CD, and test with simulated users. This DevSecOps-aligned approach ensures secure, scalable app access, preventing unauthorized entry in production environments.

34. How do you manage SSL/TLS encryption in Fastly?

• Automate SSL certificate issuance/renewals.
• Support secure TLS protocols.
• Log renewals for monitoring.
• CI/CD automates renewal workflows.
• Test certs with API checks.
• Align with DevSecOps for HTTPS.
• Ensure encrypted traffic delivery.

35. Where do you monitor WAF performance in Fastly?

Monitor WAF performance in Fastly Control Center, Prometheus for metrics, and Grafana for visualization. Log rule hits, validate configs with CI/CD, and align with DevSecOps. This ensures observable security, enabling rapid issue detection and resolution to maintain robust application protection.

36. Who troubleshoots Fastly security policy failures?

Security engineers troubleshoot WAF and Zero Trust failures, validating rules and IdP settings. SREs monitor logs, while DevOps automate tests via CI/CD. This DevSecOps-aligned collaboration ensures rapid resolution, maintaining secure policies with minimal downtime. Explore cloud security.

Edge Computing Questions

37. What are Fastly Compute@Edge capabilities?

Compute@Edge enables serverless execution (Rust, JS, Go) at the edge for dynamic content processing. Log executions, deploy via CI/CD, and test in sandbox. This DevSecOps-aligned approach ensures low-latency, scalable edge computing, supporting real-time applications with efficient, secure content modification.

38. How do you deploy Compute@Edge?

• Develop Rust/JS/Go code with Fastly CLI.
• Deploy to edge via CI/CD pipelines.
• Log execution metrics for analysis.
• Test in local sandbox environment.
• Validate with API-based tests.
• Align with DevSecOps for security.
• Ensure scalable edge execution.

39. Why does a Compute@Edge failure occur?

Compute@Edge failures stem from syntax errors, resource limits, or misconfigured logic. Validate code with Fastly CLI, log errors, and test in sandbox. CI/CD automates testing, aligning with DevSecOps to ensure reliable execution, minimizing disruptions for edge-based applications in production.

40. Where do you store state for Compute@Edge?

Store state in Fastly’s KV store or external databases like Redis. Log operations, validate configs with CI/CD, and test with simulated data. This DevSecOps-aligned approach ensures stateful, scalable edge applications, enabling efficient data management and low-latency processing for dynamic workloads.

41. Who manages Compute@Edge deployments?

DevOps engineers deploy Compute@Edge using Fastly CLI and CI/CD pipelines. SREs monitor performance, while security teams ensure compliance. Logs track deployments, and DevSecOps alignment ensures secure, scalable management, enabling reliable serverless code execution at the edge for dynamic applications.

42. Which limits affect Compute@Edge?

• CPU time limits restrict execution duration.
• Memory constraints limit script resources.
• Log execution metrics for analysis.
• CI/CD optimizes code efficiency.
• Test in sandbox for compliance.
• Align with DevSecOps for scalability.
• Ensure reliable edge performance.

43. How do you optimize Compute@Edge for performance?

Optimize Compute@Edge by minimizing subrequests, using KV caching, and logging execution times. Test with Fastly CLI, automate updates via CI/CD, and simulate workloads. This DevSecOps-aligned approach ensures low-latency edge computing, enhancing performance for real-time applications. Learn cloud security.

System Design Questions

44. How do you design a scalable Fastly CDN system?

Design a CDN with Anycast routing, edge caching, and load balancing to handle high traffic. Log metrics, automate configs via CI/CD, and test with simulated loads. This DevSecOps-aligned architecture ensures scalable, low-latency content delivery, supporting reliable performance for global applications in production.

45. What is the system design for Fastly’s Zero Trust?

• Access enforces identity-based authentication.
• Gateway filters traffic for security.
• Log access events for auditing.
• CI/CD automates policy updates.
• Test with simulated user access.
• Align with DevSecOps for security.
• Ensure enterprise-grade app protection.

46. How do you architect a DDoS mitigation system?

Architect DDoS mitigation with scrubbing centers, rate limiting, and WAF rules. Log attack patterns, automate defenses via CI/CD, and test with simulated traffic. This DevSecOps-aligned design ensures resilient, scalable protection, maintaining application availability during volumetric and app-layer attacks in production.

47. Why design a load balancer for Fastly?

A load balancer distributes traffic across origins using health checks and geo-steering for high availability. Logs monitor balancing, while CI/CD automates updates. This DevSecOps-aligned approach prevents single points of failure, optimizes traffic, and ensures reliable content delivery for global applications.

48. How do you design a low-latency DNS resolver?

• Use Anycast for proximity-based routing.
• Enable DNSSEC for secure resolutions.
• Log queries for performance analysis.
• CI/CD automates DNS updates.
• Test with dig for resolution speed.
• Align with DevSecOps for reliability.
• Ensure fast, secure DNS operations.

49. What is the architecture for Compute@Edge?

Compute@Edge uses V8 isolates for serverless Rust/JS/Go execution, with KV for state storage. Logs track performance, CI/CD automates deployments, and sandbox testing ensures reliability. This DevSecOps-aligned architecture supports scalable, low-latency edge computing for dynamic content processing in real-time applications.

50. How do you design a secure WAF system?

• Use managed rules for common threats.
• Configure custom rules for specific attacks.
• Log rule hits for analysis.
• CI/CD automates rule updates.
• Test with simulated attack traffic.
• Align with DevSecOps for security.
• Ensure robust app protection.

Understand cloud security engineering for WAF design.

Troubleshooting Questions

51. What causes a Fastly CDN outage?

CDN outages result from misconfigured VCL rules, origin failures, or routing issues. Validate headers, log cache misses, and test origins with API tools. CI/CD automates updates, while DevSecOps ensures rapid recovery, restoring reliable content delivery across Fastly’s global edge network.

52. How do you troubleshoot a DNS failure in Fastly?

• Validate records with dig or nslookup.
• Check zone configs in Control Center.
• Log resolution errors for analysis.
• CI/CD automates DNS testing.
• Test failover with API simulations.
• Align with DevSecOps for reliability.
• Minimize downtime with quick resolution.

53. Why does a WAF rule cause downtime?

WAF rules cause downtime by blocking legitimate traffic due to broad expressions or false positives. Review rules, whitelist IPs, and log blocked requests. CI/CD automates testing, while DevSecOps ensures accurate configurations, restoring access and maintaining secure, reliable application performance in production.

54. How do you debug a Compute@Edge failure?

Debug Compute@Edge failures by analyzing logs for errors, validating code with Fastly CLI, and testing in sandbox. CI/CD automates updates, ensuring reliable execution. This DevSecOps-aligned process quickly resolves issues, restoring low-latency performance for edge-based applications in production environments.

55. What causes a Zero Trust policy failure?

Zero Trust failures stem from misconfigured Access settings, IdP issues, or Gateway filtering errors. Log authentication failures, validate policies with API tests, and automate updates via CI/CD. This DevSecOps-aligned approach ensures rapid resolution, restoring secure access for production applications.

56. Where do you monitor performance issues in Fastly?

Monitor performance in Fastly Control Center, Prometheus for metrics, and Grafana for visualization. Log cache hits, latency, and errors, while CI/CD validates configs. This DevSecOps-aligned setup ensures observability, enabling rapid issue detection and resolution for reliable production operations.

57. Who handles DDoS mitigation in Fastly?

SREs configure scrubbing and WAF rules, security engineers update defenses, and DevOps automate via CI/CD. Logs track attack patterns, ensuring rapid response. This DevSecOps-aligned collaboration ensures resilient mitigation, minimizing downtime and maintaining availability. Learn cloud security.

Coding and Implementation Questions

58. How do you implement a rate limiter for Fastly?

Implement a token bucket rate limiter in Golang with Redis for distributed state to handle request bursts. Log events, test with simulated traffic via CI/CD, and align with DevSecOps. This ensures scalable, secure DDoS protection, maintaining application availability under high traffic conditions.

59. What is the complexity of Fastly’s DNS lookup?

• Uses trie for O(log n) prefix matching.
• Anycast optimizes resolution speed.
• Logs capture lookup times for analysis.
• CI/CD automates code testing.
• Test with simulated DNS queries.
• DevSecOps ensures efficient DNS.
• Delivers fast, reliable resolutions.

60. How do you code a Compute@Edge for API routing?

• Use Rust/JS for dynamic routing logic.
• Define routes in Fastly CLI.
• Log routing decisions for analysis.
• CI/CD automates deployments.
• Test in sandbox for reliability.
• Align with DevSecOps for security.
• Ensure low-latency API routing.

61. Why use Golang for Fastly’s backend systems?

Golang’s goroutines enable high-throughput, low-memory networking, ideal for Fastly’s backend. Its concurrency model supports scalable traffic handling. Logs monitor performance, while CI/CD automates deployments. This DevSecOps-aligned approach ensures efficient, reliable operations, supporting high-performance content delivery and security services.

62. How do you implement an LRU cache for CDN?

Implement an LRU cache in Golang using a hash map and doubly linked list for O(1) access. Log operations, test with simulated traffic via CI/CD, and align with DevSecOps. This ensures efficient caching, reduces latency, and enhances CDN performance for high-traffic applications.

63. How do you code a DDoS detector for Fastly?

• Use anomaly detection for traffic patterns.
• Implement in Golang with Prometheus metrics.
• Log suspicious traffic for analysis.
• CI/CD validates detection models.
• Test with simulated attack datasets.
• Align with DevSecOps for security.
• Enhance proactive DDoS mitigation.

64. How do you code a consistent hash ring for load balancing?

Code a consistent hash ring in Golang with virtual nodes for balanced traffic distribution. Log operations, test with simulated loads via CI/CD, and align with DevSecOps. This ensures scalable, reliable load balancing, minimizing disruptions and optimizing performance for Fastly’s CDN infrastructure.

Explore SRE FAQs for coding prep.

Production Questions

65. What causes a production CDN outage?

Production CDN outages stem from misconfigured VCL rules, origin failures, or routing issues. Validate headers, log cache misses, and test origins with API tools. CI/CD automates updates, while DevSecOps ensures rapid recovery, restoring reliable content delivery across Fastly’s global edge network.

66. How do you troubleshoot a production DNS failure?

• Validate records with dig or nslookup.
• Check zone configs in Control Center.
• Log resolution errors for analysis.
• CI/CD automates DNS testing.
• Test failover with API simulations.
• Align with DevSecOps for reliability.
• Minimize downtime with quick resolution.

67. Why does a production WAF rule cause downtime?

Production WAF rules cause downtime by blocking legitimate traffic due to broad expressions or false positives. Review rules, whitelist IPs, and log blocked requests. CI/CD automates testing, while DevSecOps ensures accurate configurations, restoring access and maintaining secure, reliable application performance.

68. How do you handle a production DDoS attack?

Handle DDoS attacks by enabling scrubbing, configuring WAF rules, and applying rate limiting. Log attack patterns, update defenses via CI/CD, and monitor with Prometheus. This DevSecOps-aligned approach ensures rapid, resilient mitigation, minimizing downtime and protecting critical applications.

69. What causes Compute@Edge to exceed resource limits?

• Complex logic or excessive subrequests.
• Log execution times for analysis.
• Optimize code with Fastly CLI.
• Test in sandbox for efficiency.
• Use KV store for caching.
• Align with DevSecOps for scalability.
• Ensure reliable edge performance.

70. How do you manage a production SSL certificate expiration?

Manage SSL certificate expiration with Fastly’s automated renewal system, monitoring via API checks and logging events. CI/CD automates alerts and updates, ensuring uninterrupted HTTPS. This DevSecOps-aligned approach prevents outages, maintains secure traffic encryption, and supports reliable content delivery.

71. Where do you monitor production performance issues?

Monitor performance in Fastly Control Center, Prometheus for metrics, and Grafana for visualization. Log issues, validate configs with CI/CD, and align with DevSecOps. This ensures observability, enabling rapid issue detection and resolution. Learn GitLab practices.

Advanced Questions

72. What causes a DNS failover failure in production?

DNS failover failures result from misconfigured pools, health check issues, or routing errors. Validate configs with API, log failover events, and test with simulations. CI/CD automates updates, while DevSecOps ensures reliable DNS failover, minimizing downtime and maintaining high availability.

73. How do you configure Zero Trust for production apps?

• Define Access policies with IdP integration.
• Use Gateway for secure traffic filtering.
• Log authentication events for analysis.
• CI/CD automates policy updates.
• Test with simulated user access.
• Align with DevSecOps for security.
• Ensure reliable app authentication.

74. Why does a production app show high CDN latency?

High CDN latency stems from suboptimal routing, cache misses, or origin delays. Optimize with Dynamic Content Acceleration, validate headers, and log metrics. CI/CD automates updates, while DevSecOps ensures low-latency delivery, enhancing user experience and maintaining reliable content delivery.

75. How do you debug a Compute@Edge failure?

Debug Compute@Edge failures by analyzing logs for errors, validating code with Fastly CLI, and testing in sandbox. CI/CD automates updates, ensuring reliable execution. This DevSecOps-aligned process resolves issues quickly, restoring low-latency performance for edge-based applications in production.

76. What causes a WAF false positive in production?

• Broad rule expressions misidentify traffic.
• Log blocked requests for analysis.
• Review rules in Control Center.
• Whitelist trusted IPs to prevent blocking.
• CI/CD automates rule testing.
• Align with DevSecOps for accuracy.
• Ensure reliable threat detection.

77. Where do you validate Fastly configurations?

Validate configurations in staging using Fastly API, CLI for Compute@Edge, and Control Center for DNS/WAF. Log errors, automate testing with CI/CD, and align with DevSecOps. This ensures reliable, secure configurations, preventing production issues and maintaining consistent performance across services.

78. Who manages production DDoS mitigation?

SREs configure scrubbing and WAF rules, security engineers update defenses, and DevOps automate via CI/CD. Logs track attacks, ensuring rapid response. This DevSecOps-aligned collaboration minimizes downtime, maintaining availability and resilient mitigation. Explore GitLab CI/CD.

Advanced Coding Questions

79. How do you implement a token bucket rate limiter?

Implement a token bucket rate limiter in Golang with Redis for distributed state, handling request bursts. Log events, test with simulated traffic via CI/CD, and align with DevSecOps. This ensures scalable, secure DDoS protection, maintaining application availability under high traffic conditions.

80. What is the complexity of Fastly’s BGP routing?

• Uses trie for O(log n) prefix matching.
• BGP announcements optimize routing.
• Logs capture route lookups for analysis.
• CI/CD automates code testing.
• Test with simulated BGP routes.
• DevSecOps ensures efficient routing.
• Delivers fast traffic handling.

81. How do you code a Compute@Edge for caching?

Code a Compute@Edge in Rust/JS, using KV store for caching and Fastly Cache API for responses. Log operations, test with simulated traffic via CI/CD, and align with DevSecOps. This ensures efficient caching, reduces latency, and enhances CDN performance for dynamic applications.

82. How do you optimize Compute@Edge for low latency?

Optimize Compute@Edge by minimizing subrequests, using KV caching, and logging execution times. Test with Fastly CLI, automate updates via CI/CD, and simulate workloads. This DevSecOps-aligned approach ensures low-latency edge computing, enhancing performance for real-time applications with dynamic content.

83. How do you implement a traffic anomaly detector?

• Use statistical models for anomaly detection.
• Implement in Golang with Prometheus metrics.
• Log anomalies for real-time analysis.
• CI/CD validates detection models.
• Test with simulated attack datasets.
• Align with DevSecOps for security.
• Enable proactive threat detection.

Learn GitLab CI/CD for automation.

Advanced Production Questions

84. What causes a CDN outage in production?

Production CDN outages result from misconfigured VCL rules, origin failures, or routing errors. Validate headers, log cache misses, and test origins with API tools. CI/CD automates updates, while DevSecOps ensures rapid recovery, restoring reliable content delivery across Fastly’s global edge network.

85. How do you mitigate a production DDoS attack?

• Enable scrubbing in Control Center.
• Configure WAF and rate limiting rules.
• Log attack patterns for analysis.
• CI/CD updates defense configurations.
• Monitor with Prometheus metrics.
• Align with DevSecOps for resilience.
• Minimize downtime effectively.

86. Why does Compute@Edge exceed resource limits?

Compute@Edge exceeds limits due to complex logic or excessive subrequests. Optimize with Fastly CLI, use KV caching, and log execution times. Test in sandbox, update via CI/CD, and align with DevSecOps to ensure reliable, low-latency performance for edge-based applications in production.

87. How do you troubleshoot a WAF false positive?

Troubleshoot WAF false positives by reviewing rule expressions, whitelisting IPs, and logging blocked requests. Test with safe traffic, automate updates via CI/CD, and align with DevSecOps. This ensures accurate threat detection, minimizes disruptions, and maintains secure application access in production.

88. What causes DNS propagation delays in production?

• Misconfigured TTLs or zone settings.
• Log propagation delays for analysis.
• Validate records with dig queries.
• CI/CD automates DNS updates.
• Test with API-based simulations.
• Align with DevSecOps for reliability.
• Ensure fast propagation.

89. How do you manage a production load balancer failure?

Manage load balancer failures by validating health checks, logging failover events, and testing with API simulations. Update configs via CI/CD, aligning with DevSecOps to ensure reliable traffic distribution. This restores high availability, minimizes downtime, and maintains performance for critical applications.

90. Where do you monitor real-time production metrics?

Monitor real-time metrics in Fastly Control Center, Prometheus for scrape jobs, and Grafana for visualization. Log issues, validate configs with CI/CD, and align with DevSecOps. This ensures observability, enabling rapid issue detection and resolution. Explore ArgoCD.

Interview Preparation Questions

91. What should you study for a Fastly DevOps interview?

Study Fastly’s VCL, CDN, WAF, Compute@Edge, and Zero Trust. Practice with Fastly CLI, simulate API scenarios, and learn Prometheus monitoring. Understand CI/CD and DevSecOps principles. This comprehensive preparation ensures readiness for complex, real-world DevOps scenarios in Fastly interviews.

92. Why does a production app experience high CDN latency?

High CDN latency results from suboptimal routing, cache misses, or origin delays. Optimize with Dynamic Content Acceleration, validate headers, and log metrics. CI/CD automates updates, while DevSecOps ensures low-latency delivery, enhancing user experience and maintaining reliable content delivery.

93. How do you configure real-time DDoS mitigation?

• Enable scrubbing for traffic filtering.
• Configure WAF for app-layer protection.
• Apply rate limiting to control traffic.
• Log attack patterns for analysis.
• CI/CD automates defense updates.
• Align with DevSecOps for resilience.
• Ensure robust app protection.

94. How do you debug a Compute@Edge failure?

Debug Compute@Edge failures by analyzing logs for errors, validating code with Fastly CLI, and testing in sandbox. CI/CD automates updates, ensuring reliable execution. This DevSecOps-aligned process resolves issues quickly, restoring low-latency performance for edge-based applications in production.

95. How do you troubleshoot a production DNS issue?

Troubleshoot DNS issues by validating records with dig, checking zone configs, and logging errors. Automate testing with CI/CD, test failover with API simulations, and align with DevSecOps. This ensures rapid resolution, minimizing downtime and maintaining reliable DNS performance.

96. What causes a Zero Trust failure in production?

• Misconfigured Access or IdP settings.
• Incorrect Gateway filtering rules.
• Log authentication failures for analysis.
• CI/CD automates policy testing.
• Test with simulated user access.
• Align with DevSecOps for security.
• Ensure reliable authentication.

97. Where do you test Fastly configurations?

Test configurations in staging using Fastly API, CLI for Compute@Edge, and Control Center for DNS/WAF. Log errors, automate testing with CI/CD, and align with DevSecOps. This ensures reliable, secure configurations, preventing production issues and maintaining consistent performance.

98. Who manages WAF issues in production?

Security engineers manage WAF issues, validating rules and whitelisting IPs. SREs monitor logs, while DevOps automate tests via CI/CD. Logs track performance, and DevSecOps ensures secure operations, minimizing disruptions and maintaining reliable application protection in production.

99. How do you code a rate limiter for Fastly apps?

• Implement token bucket in Golang.
• Use Redis for distributed state.
• Log rate limit events for analysis.
• CI/CD automates code testing.
• Test with simulated request bursts.
• Align with DevSecOps for security.
• Protect apps from DDoS attacks.

100. What causes a load balancer failure in production?

Load balancer failures result from misconfigured health checks, failover pool issues, or routing errors. Validate configs, log failover events, and test with API simulations. CI/CD automates updates, while DevSecOps ensures reliable traffic distribution, restoring high availability and minimizing downtime.

101. How do you optimize Compute@Edge for real-time apps?

Optimize Compute@Edge by minimizing subrequests, using KV caching, and logging execution times. Test with Fastly CLI, automate updates via CI/CD, and simulate workloads. This DevSecOps-aligned approach ensures low-latency edge computing, enhancing performance for real-time apps. Learn ELK for logging.

102. How do you simulate a DDoS attack for testing?

Simulate a DDoS attack with Locust to generate traffic against Fastly endpoints. Log attack patterns, validate WAF rules, and test via CI/CD. This DevSecOps-aligned approach ensures robust defense validation, confirming effective mitigation and maintaining application availability under attack conditions.

103. What is the role of VCL in Fastly’s edge logic?

VCL (Varnish Configuration Language) defines custom edge logic for Fastly, enabling real-time content manipulation, routing, and caching decisions. Logs track VCL performance, while CI/CD automates updates. This DevSecOps-aligned approach ensures flexible, secure configurations, supporting dynamic, scalable content delivery for complex applications.