Fastly Engineer Interview Questions with Answers [2025]

Fastly Core Concepts

1. What is Fastly and its primary role?

• Fastly is an edge cloud platform for content delivery.
• Provides real-time CDN for web acceleration.
• Supports VCL for custom configuration.
• Enables Compute@Edge with WebAssembly.
• Offers WAF for security protection.
• Integrates with DevOps for CI/CD pipelines.
• Optimizes performance with global edge network.

Learn how real-time DevOps enhances Fastly deployments.

2. Why use Fastly for DevOps security?

Fastly provides robust security for DevOps with its WAF, DDoS mitigation, and rate limiting at the edge, ensuring real-time threat protection without performance degradation. Its VCL scripting allows custom security rules, while integration with CI/CD pipelines enables automated configuration updates, making it ideal for secure, scalable infrastructure.

3. When to deploy Fastly in DevOps?

• For accelerating APIs in CI/CD workflows.
• Protecting apps from DDoS attacks.
• Implementing WAF for endpoint security.
• Optimizing media streaming in pipelines.
• Managing multi-cloud deployments.
• Ensuring compliance with audits.
• Scaling for high-traffic events.

4. Where does Fastly's edge network operate?

Fastly's edge network spans 100+ Points of Presence (PoPs) globally, processing traffic closer to users for low latency.

It ensures rapid content delivery.

5. Who uses Fastly in organizations?

• DevOps engineers for pipeline acceleration.
• Security specialists for WAF rules.
• SREs for reliability monitoring.
• Platform teams for infrastructure.
• Developers for edge functions.
• Compliance officers for logs.
• Product managers for performance.

6. Which Fastly services secure DevOps?

Fastly's WAF, DDoS protection, Next-Gen WAF, and Rate Limiting secure DevOps with real-time threat mitigation.

7. How does Fastly integrate with CI/CD?

• Uses API tokens for automation.
• Supports Terraform for IaC.
• Integrates with Jenkins/GitHub Actions.
• Triggers webhooks for events.
• Automates WAF rule updates.
• Monitors pipeline performance.
• Secures API calls in builds.

8. What is Fastly's VCL?

• VCL is Fastly's configuration language.
• Customizes request/response handling.
• Supports if/else logic for rules.
• Integrates with DevOps for automation.
• Provides real-time configuration.
• Enables custom caching policies.
• Monitors VCL performance.

Discover how GCP DevOps uses VCL scripting.

9. Why use Fastly for DDoS protection?

Fastly's DDoS protection mitigates attacks at the edge, ensuring availability with autonomous mitigation and global scale.

10. When to enable Next-Gen WAF?

• Securing APIs and web apps.
• Implementing rate limiting.
• Validating schemas in CI/CD.
• Securing production endpoints.
• Ensuring API policy compliance.
• Detecting real-time threats.
• Integrating with pipelines.

11. What is Compute@Edge?

• Serverless platform with WebAssembly.
• Executes code at the edge.
• Supports Rust, JavaScript.
• Integrates with KV storage.
• Enables A/B testing.
• Reduces latency for dynamic content.
• Scales for traffic spikes.

12. Why deploy Fastly Spectrum?

Spectrum secures non-HTTP protocols like SSH, protecting apps from DDoS with edge delivery.

13. When to use Fastly's Rate Limiting?

• Protecting APIs from abuse.
• Preventing brute force attacks.
• Throttling high-traffic endpoints.
• Securing CI/CD deployments.
• Ensuring API usage compliance.
• Managing real-time traffic spikes.
• Blocking bot-driven requests.

14. Where does Fastly Access fit?

Fastly Access enforces Zero Trust for apps, replacing VPNs with secure authentication via IdPs.

It ensures secure access control.

15. Who uses Fastly Gateway?

• Security teams for DNS filtering.
• DevOps for network security.
• SREs for threat blocking.
• Platform teams for policies.
• Compliance for audit logs.
• Developers for secure browsing.
• Admins for network segmentation.

Explore how cloud observability enhances Gateway.

16. Which protocols does Fastly secure?

Fastly secures HTTP/HTTPS, TCP, UDP, and DNS with global edge security and performance.

17. How optimize Fastly CDN?

• Caches assets at global PoPs.
• Uses VCL for custom routing.
• Compresses with Brotli.
• Optimizes images dynamically.
• Automates purging in CI/CD.
• Monitors cache hit ratios.
• Configures custom cache rules.

18. What is Fastly's Shielding?

• Reduces origin server load.
• Routes traffic to parent PoP.
• Improves cache hit ratios.
• Integrates with DevOps.
• Provides real-time analytics.
• Scales for global delivery.
• Reduces latency significantly.

19. Why use Fastly Load Balancing?

Fastly Load Balancing ensures high availability with health checks and failover for DevOps.

20. When enable Fastly's Bot Management?

• Detecting malicious bot traffic.
• Preventing automated abuse.
• Throttling bot requests.
• Securing CI/CD endpoints.
• Ensuring API compliance.
• Managing bot challenges.
• Blocking sophisticated bots.

21. What is Next-Gen WAF?

• Advanced WAF for threat protection.
• Uses ML for anomaly detection.
• Supports custom rules.
• Integrates with DevOps.
• Provides real-time intelligence.
• Blocks attacks at edge.
• Logs for compliance auditing.

22. Why use Fastly for SSL/TLS?

Fastly provides free SSL, automatic encryption, and custom ciphers for secure DevOps traffic.

Explore how Azure DevOps integrates SSL.

23. When configure VCL snippets?

• Customizing request/response handling.
• Rewriting URLs for optimization.
• Redirecting traffic dynamically.
• Securing staging environments.
• Adding security headers.
• Optimizing performance.
• Ensuring regional compliance.

24. Where deploy Fastly Compute?

Fastly Compute deploys WebAssembly modules at edge for serverless functions in DevOps.

It supports low-latency execution.

25. Who uses Fastly Images?

• Developers for image optimization.
• DevOps for asset delivery.
• Security for image scanning.
• Platform teams for CDN integration.
• Product for user experience.
• Compliance for data residency.
• Teams for asset workflows.

26. Which Fastly analytics?

Traffic, Security, and Real User Monitoring for DevOps insights and optimization.

27. How use Fastly API?

• Automates zone configurations with tokens.
• Integrates with Terraform for IaC.
• Scripts WAF updates in CI/CD.
• Monitors via API for alerting.
• Triggers webhook notifications.
• Supports bulk operations for scaling.
• Secures with scoped API keys.

28. What is Fastly's Domain Management?

• Manages secure domain registration.
• Provides WHOIS privacy.
• Integrates with DNS management.
• Supports automated transfers.
• Monitors domain threats.
• Automates renewals for compliance.
• Enables DevOps domain automation.

29. Why use Fastly DNS?

Fastly DNS resolves queries with speed, DDoS protection, and automation for DevOps networks.

30. When enable Under Attack?

• Mitigating DDoS attacks dynamically.
• Responding to real-time threats.
• Implementing JS challenges.
• Protecting CI/CD deployments.
• Safeguarding high-traffic events.
• Ensuring security compliance.
• Blocking malicious traffic.

Learn how DevOps FAQs address attack mitigation.

31. What is Fastly Access?

• Zero Trust for secure app access.
• Integrates with SSO providers.
• Enforces least privilege policies.
• Logs access for auditing.
• Scales for enterprise users.
• Replaces VPN for remote work.
• Verifies identities in real-time.

32. Why use Fastly Gateway?

Gateway filters DNS/HTTP traffic, blocking threats for secure DevOps network access.

33. When configure Firewall Rules?

• Controlling IP-based access.
• Blocking by country or agent.
• Filtering malicious traffic.
• Automating rules in CI/CD.
• Ensuring data law compliance.
• Responding to real-time threats.
• Managing bot traffic.

34. Where use Fastly Cache?

Fastly Cache stores static assets at edge, reducing origin load for DevOps performance.

Supports dynamic purging.

35. Who uses Fastly Analytics?

• DevOps for traffic metrics.
• Security for threat insights.
• SREs for uptime monitoring.
• Platform teams for analysis.
• Developers for optimization.
• Compliance for audit logs.
• Product for user behavior.

Explore how interview prep covers analytics.

36. Which encryption features?

TLS 1.3, custom certificates, and cipher suites for secure DevOps traffic.

37. How support GitOps?

• Uses Terraform for IaC.
• Versions configs in Git.
• Automates CI/CD deployments.
• Triggers webhooks for events.
• Secures pipeline integrations.
• Supports ArgoCD workflows.
• Scales for GitOps automation.

38. What is Fastly Shielding?

• Reduces origin server load.
• Routes traffic to parent PoP.
• Improves cache hit ratios.
• Integrates with DevOps.
• Provides real-time analytics.
• Scales for global delivery.
• Reduces latency significantly.

39. Why use Fastly Load Balancing?

Fastly Load Balancing ensures high availability with health checks and failover for DevOps.

40. When enable Bot Management?

• Detecting malicious bot traffic.
• Preventing automated abuse.
• Throttling bot requests.
• Securing CI/CD endpoints.
• Ensuring API compliance.
• Managing bot challenges.
• Blocking sophisticated bots.

41. What is Next-Gen WAF?

• Advanced WAF for threat protection.
• Uses ML for anomaly detection.
• Supports custom rules.
• Integrates with DevOps.
• Provides real-time intelligence.
• Blocks attacks at edge.
• Logs for compliance auditing.

42. Why use Fastly for SSL/TLS?

Fastly provides free SSL, automatic encryption, and custom ciphers for secure DevOps traffic.

Explore how Azure DevOps integrates SSL.

43. When configure VCL snippets?

• Customizing request/response handling.
• Rewriting URLs for optimization.
• Redirecting traffic dynamically.
• Securing staging environments.
• Adding security headers.
• Optimizing performance.
• Ensuring regional compliance.

44. Where deploy Fastly Compute?

Fastly Compute deploys WebAssembly modules at edge for serverless functions in DevOps.

It supports low-latency execution.

45. Who uses Fastly Images?

• Developers for image optimization.
• DevOps for asset delivery.
• Security for image scanning.
• Platform teams for CDN integration.
• Product for user experience.
• Compliance for data residency.
• Teams for asset workflows.

46. Which Fastly analytics?

Traffic, Security, and Real User Monitoring for DevOps insights and optimization.

47. How use Fastly API?

• Automates zone configurations with tokens.
• Integrates with Terraform for IaC.
• Scripts WAF updates in CI/CD.
• Monitors via API for alerting.
• Triggers webhook notifications.
• Supports bulk operations for scaling.
• Secures with scoped API keys.

48. What is Fastly's Domain Management?

• Manages secure domain registration.
• Provides WHOIS privacy.
• Integrates with DNS management.
• Supports automated transfers.
• Monitors domain threats.
• Automates renewals for compliance.
• Enables DevOps domain automation.

49. Why use Fastly DNS?

Fastly DNS resolves queries with speed, DDoS protection, and automation for DevOps networks.

50. When enable Under Attack?

• Mitigating DDoS attacks dynamically.
• Responding to real-time threats.
• Implementing JS challenges.
• Protecting CI/CD deployments.
• Safeguarding high-traffic events.
• Ensuring security compliance.
• Blocking malicious traffic.

Learn how DevOps FAQs address attack mitigation.

51. What is Fastly Access?

• Zero Trust for secure app access.
• Integrates with SSO providers.
• Enforces least privilege policies.
• Logs access for auditing.
• Scales for enterprise users.
• Replaces VPN for remote work.
• Verifies identities in real-time.

52. Why use Fastly Gateway?

Gateway filters DNS/HTTP traffic, blocking threats for secure DevOps network access.

53. When configure Firewall Rules?

• Controlling IP-based access.
• Blocking by country or agent.
• Filtering malicious traffic.
• Automating rules in CI/CD.
• Ensuring data law compliance.
• Responding to real-time threats.
• Managing bot traffic.

54. Where use Fastly Cache?

Fastly Cache stores static assets at edge, reducing origin load for DevOps performance.

Supports dynamic purging.

55. Who uses Fastly Analytics?

• DevOps for traffic metrics.
• Security for threat insights.
• SREs for uptime monitoring.
• Platform teams for analysis.
• Developers for optimization.
• Compliance for audit logs.
• Product for user behavior.

Explore how interview prep covers analytics.

56. Which encryption features?

TLS 1.3, custom certificates, and cipher suites for secure DevOps traffic.

57. How support GitOps?

• Uses Terraform for IaC.
• Versions configs in Git.
• Automates CI/CD deployments.
• Triggers webhooks for events.
• Secures pipeline integrations.
• Supports ArgoCD workflows.
• Scales for GitOps automation.

58. What is Fastly Shielding?

• Reduces origin server load.
• Routes traffic to parent PoP.
• Improves cache hit ratios.
• Integrates with DevOps.
• Provides real-time analytics.
• Scales for global delivery.
• Reduces latency significantly.

59. Why use Fastly Load Balancing?

Fastly Load Balancing ensures high availability with health checks and failover for DevOps.

60. When enable Bot Management?

• Detecting malicious bot traffic.
• Preventing automated abuse.
• Throttling bot requests.
• Securing CI/CD endpoints.
• Ensuring API compliance.
• Managing bot challenges.
• Blocking sophisticated bots.

Learn how advanced DevOps manages bots.

61. What is Next-Gen WAF?

• Advanced WAF for threat protection.
• Uses ML for anomaly detection.
• Supports custom rules.
• Integrates with DevOps.
• Provides real-time intelligence.
• Blocks attacks at edge.
• Logs for compliance auditing.

62. Why use Fastly for SSL/TLS?

Fastly provides free SSL, automatic encryption, and custom ciphers for secure DevOps traffic.

63. When configure VCL snippets?

• Customizing request/response handling.
• Rewriting URLs for optimization.
• Redirecting traffic dynamically.
• Securing staging environments.
• Adding security headers.
• Optimizing performance.
• Ensuring regional compliance.

64. Where deploy Fastly Compute?

Fastly Compute deploys WebAssembly modules at edge for serverless functions in DevOps.

It supports low-latency execution.

65. Who uses Fastly Images?

• Developers for image optimization.
• DevOps for asset delivery.
• Security for image scanning.
• Platform teams for CDN integration.
• Product for user experience.
• Compliance for data residency.
• Teams for asset workflows.

66. Which Fastly analytics?

Traffic, Security, and Real User Monitoring for DevOps insights and optimization.

67. How use Fastly API?

• Automates zone configurations with tokens.
• Integrates with Terraform for IaC.
• Scripts WAF updates in CI/CD.
• Monitors via API for alerting.
• Triggers webhook notifications.
• Supports bulk operations for scaling.
• Secures with scoped API keys.

68. What is Fastly's Domain Management?

• Manages secure domain registration.
• Provides WHOIS privacy.
• Integrates with DNS management.
• Supports automated transfers.
• Monitors domain threats.
• Automates renewals for compliance.
• Enables DevOps domain automation.

69. Why use Fastly DNS?

Fastly DNS resolves queries with speed, DDoS protection, and automation for DevOps networks.

70. When enable Under Attack?

• Mitigating DDoS attacks dynamically.
• Responding to real-time threats.
• Implementing JS challenges.
• Protecting CI/CD deployments.
• Safeguarding high-traffic events.
• Ensuring security compliance.
• Blocking malicious traffic.

Learn how DevOps FAQs address attack mitigation.

71. What is Fastly Access?

• Zero Trust for secure app access.
• Integrates with SSO providers.
• Enforces least privilege policies.
• Logs access for auditing.
• Scales for enterprise users.
• Replaces VPN for remote work.
• Verifies identities in real-time.

72. Why use Fastly Gateway?

Gateway filters DNS/HTTP traffic, blocking threats for secure DevOps network access.

73. When configure Firewall Rules?

• Controlling IP-based access.
• Blocking by country or agent.
• Filtering malicious traffic.
• Automating rules in CI/CD.
• Ensuring data law compliance.
• Responding to real-time threats.
• Managing bot traffic.

74. Where use Fastly Cache?

Fastly Cache stores static assets at edge, reducing origin load for DevOps performance.

Supports dynamic purging.

75. Who uses Fastly Analytics?

• DevOps for traffic metrics.
• Security for threat insights.
• SREs for uptime monitoring.
• Platform teams for analysis.
• Developers for optimization.
• Compliance for audit logs.
• Product for user behavior.

Explore how interview prep covers analytics.

76. Which encryption features?

TLS 1.3, custom certificates, and cipher suites for secure DevOps traffic.

77. How support GitOps?

• Uses Terraform for IaC.
• Versions configs in Git.
• Automates CI/CD deployments.
• Triggers webhooks for events.
• Secures pipeline integrations.
• Supports ArgoCD workflows.
• Scales for GitOps automation.

78. What is Fastly Shielding?

• Reduces origin server load.
• Routes traffic to parent PoP.
• Improves cache hit ratios.
• Integrates with DevOps.
• Provides real-time analytics.
• Scales for global delivery.
• Reduces latency significantly.

79. Why use Fastly Load Balancing?

Fastly Load Balancing ensures high availability with health checks and failover for DevOps.

80. When enable Bot Management?

• Detecting malicious bot traffic.
• Preventing automated abuse.
• Throttling bot requests.
• Securing CI/CD endpoints.
• Ensuring API compliance.
• Managing bot challenges.
• Blocking sophisticated bots.

81. What is Next-Gen WAF?

• Advanced WAF for threat protection.
• Uses ML for anomaly detection.
• Supports custom rules.
• Integrates with DevOps.
• Provides real-time intelligence.
• Blocks attacks at edge.
• Logs for compliance auditing.

82. Why use Fastly for SSL/TLS?

Fastly provides free SSL, automatic encryption, and custom ciphers for secure DevOps traffic.

83. When configure VCL snippets?

• Customizing request/response handling.
• Rewriting URLs for optimization.
• Redirecting traffic dynamically.
• Securing staging environments.
• Adding security headers.
• Optimizing performance.
• Ensuring regional compliance.

84. Where deploy Fastly Compute?

Fastly Compute deploys WebAssembly modules at edge for serverless functions in DevOps.

It supports low-latency execution.

85. Who uses Fastly Images?

• Developers for image optimization.
• DevOps for asset delivery.
• Security for image scanning.
• Platform teams for CDN integration.
• Product for user experience.
• Compliance for data residency.
• Teams for asset workflows.

Explore how advanced DevOps optimizes images.

86. Which Fastly analytics?

Traffic, Security, and Real User Monitoring for DevOps insights and optimization.

87. How use Fastly API?

• Automates zone configurations with tokens.
• Integrates with Terraform for IaC.
• Scripts WAF updates in CI/CD.
• Monitors via API for alerting.
• Triggers webhook notifications.
• Supports bulk operations for scaling.
• Secures with scoped API keys.

88. What is Fastly's Domain Management?

• Manages secure domain registration.
• Provides WHOIS privacy.
• Integrates with DNS management.
• Supports automated transfers.
• Monitors domain threats.
• Automates renewals for compliance.
• Enables DevOps domain automation.

89. Why use Fastly DNS?

Fastly DNS resolves queries with speed, DDoS protection, and automation for DevOps networks.

90. When enable Under Attack?

• Mitigating DDoS attacks dynamically.
• Responding to real-time threats.
• Implementing JS challenges.
• Protecting CI/CD deployments.
• Safeguarding high-traffic events.
• Ensuring security compliance.
• Blocking malicious traffic.

91. What is Fastly Access?

• Zero Trust for secure app access.
• Integrates with SSO providers.
• Enforces least privilege policies.
• Logs access for auditing.
• Scales for enterprise users.
• Replaces VPN for remote work.
• Verifies identities in real-time.

92. Why use Fastly Gateway?

Gateway filters DNS/HTTP traffic, blocking threats for secure DevOps network access.

93. When configure Firewall Rules?

• Controlling IP-based access.
• Blocking by country or agent.
• Filtering malicious traffic.
• Automating rules in CI/CD.
• Ensuring data law compliance.
• Responding to real-time threats.
• Managing bot traffic.

94. Where use Fastly Cache?

Fastly Cache stores static assets at edge, reducing origin load for DevOps performance.

Supports dynamic purging.

95. Who uses Fastly Analytics?

• DevOps for traffic metrics.
• Security for threat insights.
• SREs for uptime monitoring.
• Platform teams for analysis.
• Developers for optimization.
• Compliance for audit logs.
• Product for user behavior.

Explore how interview prep covers analytics.

96. Which encryption features?

TLS 1.3, custom certificates, and cipher suites for secure DevOps traffic.

97. How support GitOps?

• Uses Terraform for IaC.
• Versions configs in Git.
• Automates CI/CD deployments.
• Triggers webhooks for events.
• Secures pipeline integrations.
• Supports ArgoCD workflows.
• Scales for GitOps automation.

98. What is Fastly Shielding?

• Reduces origin server load.
• Routes traffic to parent PoP.
• Improves cache hit ratios.
• Integrates with DevOps.
• Provides real-time analytics.
• Scales for global delivery.
• Reduces latency significantly.

99. Why use Fastly Load Balancing?

Fastly Load Balancing ensures high availability with health checks and failover for DevOps.

Learn how scenario-based DevOps uses Load Balancing.

100. When enable Bot Management?

• Detecting malicious bot traffic.
• Preventing automated abuse.
• Throttling bot requests.
• Securing CI/CD endpoints.
• Ensuring API compliance.
• Managing bot challenges.
• Blocking sophisticated bots.

101. What is Next-Gen WAF?

• Advanced WAF for threat protection.
• Uses ML for anomaly detection.
• Supports custom rules.
• Integrates with DevOps.
• Provides real-time intelligence.
• Blocks attacks at edge.
• Logs for compliance auditing.

102. Why use Fastly for SSL/TLS?

Fastly provides free SSL, automatic encryption, and custom ciphers for secure DevOps traffic.

103. When configure VCL snippets?

• Customizing request/response handling.
• Rewriting URLs for optimization.
• Redirecting traffic dynamically.
• Securing staging environments.
• Adding security headers.
• Optimizing performance.
• Ensuring regional compliance.