75+ Kong Interview Questions and Answers [API Gateway]

Kong Architecture

1. What is Kong API Gateway and its core components?

Kong API Gateway is an open-source platform for managing APIs. Core components include:

• Proxy for traffic routing.
• Services for backend definitions.
• Routes for endpoint mapping.
• Plugins for functionality.
• Consumers for authentication.
• Integration with CI/CD pipelines.
• Admin API for management.

Kong simplifies API orchestration.

2. Why is Kong suitable for microservices?

Kong excels in microservices by providing centralized routing, rate limiting, and security. It supports dynamic service discovery, scales horizontally, and integrates with Kubernetes. By decoupling API logic from applications, Kong reduces complexity, enhances observability, and ensures consistent governance across distributed systems, making it ideal for modern DevOps environments.

3. When should Kong be deployed?

Deploy Kong when:

• Managing multiple APIs.
• Requiring traffic control.
• Enforcing security policies.
• Integrating with Kubernetes.
• Versioning configs in Git.
• Monitoring performance.
• Scaling for traffic.

This centralizes API management.

4. Where does Kong store configurations?

Kong stores configurations in:

• Database like PostgreSQL.
• Git for declarative files.
• CI/CD pipeline scripts.
• Monitored service dashboards.
• External config tools.
• API-driven endpoints.
• Backup systems.

This ensures consistency.

5. Who manages Kong in DevOps?

DevOps engineers manage Kong. They:

• Configure services and routes.
• Install plugins for features.
• Integrate with pipelines.
• Monitor traffic metrics.
• Version in Git.
• Handle scaling.
• Troubleshoot issues.

This maintains API reliability.

6. Which database is recommended for Kong?

PostgreSQL is recommended for Kong, offering:

• High availability support.
• Integration with plugins.
• Versioning in Git.
• Monitored query performance.
• Scalable storage.
• Backup capabilities.
• Transaction safety.

This supports production.

7. How does Kong process requests?

Kong processes requests by:

• Matching routes to services.
• Applying plugin middleware.
• Proxying to backends.
• Versioning in Git.
• Monitoring flow metrics.
• Scaling for load.
• Handling errors.

Example: ```yaml services: - name: example url: http://backend:8080 ``` This, with OpenShift, ensures efficient handling.

Services and Routes

8. What is a Kong service?

A Kong service represents a backend API. It includes:

• URL for upstream.
• Protocol configurations.
• Integration with routes.
• Versioning in Git.
• Monitored health.
• Scalable endpoints.
• Plugin attachments.

Services define backends.

9. Why define routes in Kong?

Routes map incoming requests to services, enabling path-based routing. They support methods, headers, and hosts, reducing complexity by 40%. Integration with CI/CD ensures dynamic updates, making Kong suitable for microservices governance.

10. When to use host-based routing?

Use host-based routing when:

• Mapping domains to services.
• Handling multi-tenant APIs.
• Integrating with DNS.
• Versioning in Git.
• Monitoring traffic.
• Scaling for domains.
• Troubleshoot mismatches.

This simplifies mapping.

11. Where are routes configured?

Routes are configured in:

• Kong Admin API.
• Declarative YAML files.
• Git repositories.
• CI/CD pipelines.
• Monitored dashboards.
• External tools.
• Database schemas.

This enables management.

12. Who configures Kong routes?

API engineers configure routes. They:

• Define path/method matches.
• Test in staging.
• Integrate with services.
• Monitor routing metrics.
• Version in Git.
• Handle updates.
• Optimize for performance.

This ensures accurate mapping.

13. Which route attribute matches methods?

methods attribute matches HTTP methods, offering:

• GET, POST, PUT support.
• Integration with plugins.
• Versioning in Git.
• Monitored matches.
• Scalable routing.
• Custom method handling.
• Security filtering.

This controls access.

14. How do you update routes dynamically?

Update routes by:

• Using Admin API calls.
• Applying declarative configs.
• Testing in staging.
• Versioning in Git.
• Monitoring changes.
• Handling rollbacks.
• Integrating with CI/CD.

This maintains flexibility.

15. What challenges arise with route conflicts?

Route conflicts cause incorrect traffic routing. Overlapping paths lead to errors. Engineers define specific matches, test in staging, and monitor logs. Integration with OpenShift ensures validation, preventing disruptions.

Plugins and Extensions

16. What are Kong plugins?

Kong plugins extend functionality. They include:

• Rate limiting for control.
• Authentication for security.
• Logging for observability.
• Versioning in Git.
• Monitored plugin performance.
• Scalable middleware.
• Custom development.

Plugins enhance Kong.

17. Why use rate limiting plugins?

Rate limiting prevents abuse, ensuring fair usage. It supports algorithms like token bucket, integrates with consumers, and reduces load by 30%. Monitoring usage aligns with DevOps for secure, scalable APIs.

18. When to enable authentication plugins?

Enable authentication when:

• Securing API endpoints.
• Supporting OAuth/JWT.
• Integrating with consumers.
• Versioning in Git.
• Monitoring access.
• Scaling for users.
• Troubleshooting tokens.

This protects resources.

19. Where are plugins attached?

Plugins are attached to:

• Services or routes.
• Consumers for access.
• Global configurations.
• Git-versioned files.
• Monitored entities.
• API endpoints.
• External schemas.

This scopes functionality.

20. Who develops custom plugins?

Plugin developers create custom plugins. They:

• Write Lua code.
• Test in staging.
• Integrate with Kong.
• Monitor performance.
• Version in Git.
• Handle schemas.
• Optimize logic.

This extends capabilities.

21. Which plugin handles CORS?

CORS plugin handles cross-origin requests, offering:

• Header additions.
• Origin validation.
• Integration with services.
• Versioning in Git.
• Monitored requests.
• Scalable handling.
• Custom configs.

This enables web apps.

22. How do you enable a plugin?

Enable a plugin by:

• Using Admin API POST.
• Applying declarative YAML.
• Testing in staging.
• Versioning in Git.
• Monitoring activation.
• Handling configs.
• Integrating with routes.

This activates features.

23. What are the steps to create a custom plugin?

Creating a custom plugin extends Kong. Developers write Lua handlers, define schemas, test in staging, and integrate with CI/CD. Versioning in Git ensures traceability, while monitoring performance aligns with DevOps for scalable, secure API management.

Security and Authentication

24. What is Kong's authentication mechanism?

Kong's authentication uses plugins for OAuth, JWT, basic auth. It includes:

• Consumer token validation.
• Integration with external providers.
• Versioning in Git.
• Monitored access logs.
• Scalable token handling.
• Custom credential storage.
• Revocation support.

This secures APIs.

25. Why implement OAuth in Kong?

OAuth secures APIs with delegated access, supporting scopes and tokens. It integrates with providers, reduces credential exposure, and aligns with DevSecOps for compliant, scalable authentication in microservices.

26. When to use JWT plugins?

Use JWT plugins when:

• Stateless token validation needed.
• Integrating with identity providers.
• Handling microservices auth.
• Versioning in Git.
• Monitoring token expiry.
• Scaling for users.
• Troubleshooting signatures.

This enables secure access.

27. Where are credentials stored?

Credentials are stored in:

• Kong database.
• External vaults like HashiCorp Vault.
• Git-versioned configs.
• Monitored secure stores.
• API endpoints.
• Consumer objects.
• Backup systems.

This ensures security.

28. Who configures authentication?

Security engineers configure authentication. They:

• Enable OAuth/JWT plugins.
• Test token flows.
• Integrate with providers.
• Monitor access patterns.
• Version in Git.
• Handle revocation.
• Optimize for performance.

This protects APIs.

29. Which plugin enforces ACLs?

ACL plugin enforces access control, offering:

• Group-based permissions.
• Integration with consumers.
• Versioning in Git.
• Monitored access.
• Scalable rule handling.
• Custom group configs.
• Policy enforcement.

This controls access.

30. How do you revoke tokens?

Revoke tokens by:

• Using Admin API DELETE.
• Updating consumer credentials.
• Testing revocation.
• Versioning in Git.
• Monitoring revocations.
• Handling propagation.
• Integrating with providers.

This secures systems.

31. What are the steps to set up OAuth?

Setting up OAuth secures APIs. Engineers enable plugins, configure providers, test flows, and monitor access. Versioning in Git ensures traceability, while integration with CI/CD automates updates, aligning with DevSecOps for scalable, compliant authentication.

32. Why do authentication plugins fail?

Authentication plugins fail due to invalid tokens or misconfigured providers. Expired credentials or scope mismatches cause issues. Engineers validate configs, monitor logs, and version changes in Git. Integration with cloud tools provides insights, ensuring reliable access control.

Rate Limiting and Traffic Control

33. What is rate limiting in Kong?

Rate limiting controls request frequency. It includes:

• Token bucket algorithm.
• Consumer-based limits.
• Integration with plugins.
• Versioning in Git.
• Monitored rate metrics.
• Scalable enforcement.
• Burst handling.

Rate limiting prevents abuse.

34. Why implement rate limiting?

Rate limiting protects APIs from overload, ensuring availability. It supports fair usage, integrates with authentication, and reduces costs by 25%. Monitoring limits aligns with DevSecOps for secure, scalable traffic management in microservices.

35. When to use burst limits?

Use burst limits when:

• Allowing short spikes.
• Balancing fairness.
• Integrating with consumers.
• Versioning in Git.
• Monitoring bursts.
• Scaling for traffic.
• Troubleshooting limits.

This accommodates peaks.

36. Where are rate limits configured?

Rate limits are configured in:

• Plugin settings.
• Consumer attributes.
• Git-versioned files.
• CI/CD scripts.
• Monitored dashboards.
• API endpoints.
• External tools.

This scopes control.

37. Who sets rate limits?

API architects set rate limits. They:

• Define thresholds.
• Test in staging.
• Integrate with plugins.
• Monitor usage.
• Version in Git.
• Adjust for apps.
• Handle violations.

This ensures fairness.

38. Which algorithm uses Kong for limiting?

Token bucket algorithm uses Kong for limiting, offering:

• Burst and steady rate support.
• Integration with consumers.
• Versioning in Git.
• Monitored bucket levels.
• Scalable enforcement.
• Custom window sizes.
• Refill logic.

This balances traffic.

39. How do you monitor rate limits?

Monitor rate limits by:

• Using Kong metrics.
• Integrating with Prometheus.
• Setting alerts.
• Testing in staging.
• Versioning in Git.
• Analyzing usage.
• Scaling monitoring.

This tracks compliance.

40. What are the steps to configure rate limiting?

Configuring rate limiting prevents API abuse. Architects enable plugins, define thresholds, test in staging, and monitor metrics. Versioning in Git ensures traceability, while integration with CI/CD automates updates, aligning with DevSecOps for secure, scalable traffic management in microservices environments.

41. Why do rate limits cause 429 errors?

Rate limits cause 429 errors when thresholds are exceeded. Misconfigured buckets or consumer mismatches trigger responses. Engineers adjust limits, monitor usage, and version changes in Git. Integration with cloud platforms provides insights, ensuring fair usage and minimal disruptions.

Observability and Monitoring

42. What is Kong's observability?

Kong's observability tracks metrics and logs. It includes:

• Request/response metrics.
• Plugin execution logs.
• Integration with Prometheus.
• Versioning in Git.
• Monitored dashboards.
• Scalable data collection.
• Custom metrics.

Observability provides insights.

43. Why monitor Kong metrics?

Monitoring Kong metrics detects bottlenecks, ensuring reliability. It tracks latency, errors, and throughput, reducing downtime by 25%. Integration with Grafana enables visualization, aligning with DevOps for proactive management in microservices.

44. When to use Prometheus with Kong?

Use Prometheus with Kong when:

• Collecting request metrics.
• Integrating with Grafana.
• Setting latency alerts.
• Versioning in Git.
• Monitoring plugin performance.
• Scaling for traffic.
• Troubleshooting issues.

This enables observability.

45. Where are Kong metrics exported?

Kong metrics are exported to:

• Prometheus endpoints.
• Grafana for visualization.
• Cloud monitoring tools.
• Git-versioned configs.
• Monitored dashboards.
• Log aggregation systems.
• External observability.

This facilitates analysis.

46. Who sets up Kong monitoring?

Observability engineers set up monitoring. They:

• Configure Prometheus scrapes.
• Build Grafana dashboards.
• Test metric collection.
• Integrate with CI/CD.
• Version in Git.
• Monitor metrics.
• Handle alerts.

This ensures visibility.

47. Which metric tracks API latency?

request_latency tracks API latency, offering:

• Percentile measurements.
• Integration with Prometheus.
• Versioning in Git.
• Monitored thresholds.
• Scalable tracking.
• Alerting on spikes.
• Analysis tools.

This measures performance.

48. How do you integrate Kong with Grafana?

Integrate Kong with Grafana by:

• Enabling Prometheus exporter.
• Adding Grafana data source.
• Querying Kong metrics.
• Building dashboards.
• Versioning in Git.
• Setting alerts.
• Monitoring traffic.

This visualizes data.

49. What are the steps to set up logging?

Setting up logging ensures observability. Engineers enable plugins, configure endpoints, test in staging, and monitor streams. Versioning in Git tracks changes, while integration with SIEM supports compliance. This process provides detailed insights, aligning with DevOps for proactive issue resolution and performance tracking.

50. Why do metrics stop collecting?

Metrics stop collecting due to exporter errors or config changes. Misconfigured endpoints cause issues. Engineers verify Prometheus scrapes, monitor logs, and version fixes in Git. Integration with cloud tools restores observability, ensuring reliable monitoring.

Advanced Scenarios

51. What do you do for high latency in Kong?

For high latency, identify bottlenecks. Steps include:

• Analyze request_latency metrics.
• Review plugin chains.
• Test in staging.
• Version fixes in Git.
• Monitor improvements.
• Optimize upstreams.
• Scale nodes.

This restores performance.

52. Why does Kong return 502 errors?

502 errors indicate upstream failures. Plugin misconfigs or unhealthy backends cause them. Monitoring health checks and logs, integrated with GitOps, resolves issues.

53. When to use Kong for A/B testing?

Use Kong for A/B testing when:

• Routing based on headers.
• Integrating with plugins.
• Testing variants.
• Versioning in Git.
• Monitoring conversions.
• Scaling for users.
• Handling rollouts.

This enables experimentation.

54. Where are A/B configs stored?

A/B configs are stored in:

• Plugin settings.
• Git repositories.
• CI/CD scripts.
• Monitored services.
• Versioned files.
• API endpoints.
• External databases.

This manages variants.

55. Who implements A/B testing?

API developers implement A/B testing. They:

• Configure routing plugins.
• Test variants in staging.
• Integrate with analytics.
• Monitor metrics.
• Version in Git.
• Handle traffic splits.
• Analyze results.

This drives optimization.

56. Which plugin supports A/B routing?

Request terminator plugin supports A/B routing, offering:

• Header-based splits.
• Integration with services.
• Versioning in Git.
• Monitored traffic.
• Scalable splits.
• Custom logic.
• Variant handling.

This enables testing.

57. How do you monitor A/B test performance?

Monitor A/B performance by:

• Using Kong metrics.
• Integrating with Grafana.
• Tracking conversion rates.
• Testing in staging.
• Versioning in Git.
• Analyzing traffic.
• Scaling monitoring.

This validates experiments.

58. What are the steps to set up A/B testing?

Setting up A/B testing involves defining splits, configuring plugins, and monitoring results. Developers use request terminator, test in staging, and analyze metrics. Versioning in Git ensures traceability, while integration with CI/CD automates updates. This process supports data-driven decisions, enhancing application optimization and user experience.

59. Why does A/B routing fail?

A/B routing fails due to plugin misconfigs or header mismatches. Incorrect splits cause uneven traffic. Engineers validate logic, monitor metrics, and version changes in Git. Integration with cloud tools provides insights, ensuring accurate testing and reliable performance.

Real-World Scenarios

60. What do you do for Kong plugin conflicts?

For plugin conflicts, prioritize order. Steps include:

• Review plugin chain.
• Test in staging.
• Adjust plugin sequence.
• Version in Git.
• Monitor performance.
• Handle middleware.
• Resolve dependencies.

This ensures smooth execution.

61. Why does Kong scale horizontally?

Kong scales horizontally by adding nodes, sharing database state. It supports load balancing, integrates with Kubernetes, and reduces single-point failures. Monitoring node health ensures reliability in high-traffic scenarios.

62. When to use Kong in Kubernetes?

Use Kong in Kubernetes when:

• Exposing services.
• Managing ingress.
• Integrating with plugins.
• Versioning in Git.
• Monitoring pods.
• Scaling deployments.
• Troubleshooting ingress.

This centralizes API management.

63. Where are Kong configs in Kubernetes?

Kong configs in Kubernetes are in:

• ConfigMaps for VCL.
• Git repositories.
• Helm charts.
• Monitored deployments.
• Versioned manifests.
• API server storage.
• External databases.

This manages state.

64. Who deploys Kong in Kubernetes?

Platform engineers deploy Kong. They:

• Install via Helm.
• Configure ingress.
• Test in staging.
• Integrate with services.
• Version in Git.
• Monitor pods.
• Handle scaling.

This ensures API gateway.

65. Which Helm chart installs Kong?

Kong Helm chart installs Kong, offering:

• Deployment templates.
• Plugin configurations.
• Versioning in Git.
• Monitored installs.
• Scalable resources.
• Custom values.
• Integration with K8s.

This simplifies setup.

66. How do you expose Kong services?

Expose Kong services by:

• Using Ingress resources.
• Configuring LoadBalancer.
• Testing in staging.
• Versioning in Git.
• Monitoring exposure.
• Handling TLS.
• Scaling ingress.

This enables access.

67. What are the steps to integrate Kong with Kubernetes?

Integrating Kong with Kubernetes centralizes API management. Engineers install via Helm, configure ingress, test in staging, and monitor pods. Versioning in Git ensures traceability, while scaling deployments supports growth. This process aligns with cloud-native practices for scalable, secure API orchestration.

68. Why does Kong integration fail in Kubernetes?

Kong integration fails due to misconfigured Helm values or database connectivity. Pod scheduling issues cause disruptions. Engineers verify configs, monitor logs, and version changes in Git. Integration with Kubernetes tools ensures successful deployment.

Real-World Scenarios

69. What do you do for high error rates in Kong?

For high error rates, isolate causes. Steps include:

• Analyze request_error metrics.
• Review plugin configs.
• Test in staging.
• Version fixes in Git.
• Monitor reductions.
• Optimize upstreams.
• Scale nodes.

This restores reliability.

70. Why does Kong return 404 errors?

404 errors result from missing routes or services. Misconfigured paths cause issues. Monitoring logs and validating configs, integrated with PlatformOps, resolves problems.

71. When to use Kong for load balancing?

Use Kong for load balancing when:

• Distributing traffic.
• Integrating with upstreams.
• Testing health checks.
• Versioning in Git.
• Monitoring balance.
• Scaling for traffic.
• Troubleshooting imbalances.

This ensures even distribution.

72. Where are upstream configs stored?

Upstream configs are stored in:

• Kong database.
• Git repositories.
• CI/CD scripts.
• Monitored services.
• Versioned files.
• API endpoints.
• External tools.

This manages targets.

73. Who configures upstreams?

API engineers configure upstreams. They:

• Define target servers.
• Test health checks.
• Integrate with routes.
• Monitor status.
• Version in Git.
• Handle scaling.
• Optimize weights.

This balances load.

74. Which upstream feature supports health checks?

Health checks support monitoring, offering:

• Passive/active probes.
• Integration with Kong.
• Versioning in Git.
• Monitored status.
• Scalable targets.
• Custom intervals.
• Failover logic.

This ensures availability.

75. How do you scale Kong for traffic?

Scale Kong by:

• Adding horizontal nodes.
• Using load balancers.
• Testing in staging.
• Versioning in Git.
• Monitoring capacity.
• Handling database.
• Integrating with K8s.

This handles growth.

76. What are the steps to deploy Kong in Kubernetes?

Deploying Kong in Kubernetes centralizes API management. Engineers use Helm charts, configure ingress, test in staging, and monitor pods. Versioning in Git ensures traceability, while scaling deployments supports growth. This process aligns with cloud-native practices for scalable, secure API orchestration.

77. Why does Kong scaling fail?

Kong scaling fails due to database bottlenecks or node misconfigs. Overloaded Postgres causes issues. Monitoring metrics and optimizing, versioned in GitOps, resolves problems.