Application Programming Interface Security and Architecture Questions

Design and implementation of secure application programming interfaces and service interfaces, covering architecture, design patterns, and operational controls across monoliths, microservices, and service mesh environments. Topics include authentication and authorization patterns for endpoints such as OAuth two, application programming interface keys, and JavaScript Object Notation Web Tokens; token and key lifecycle and secure storage; mutual Transport Layer Security for service to service authentication; gateway and proxy based controls and hardening; input validation, schema and contract validation, output encoding, parameter filtering, and secure error handling to prevent injection, parameter pollution, and excessive data exposure. Also covers rate limiting, throttling, and anomaly detection to mitigate abuse and credential stuffing; secure transport and encryption in transit and at rest; design of internal versus external trust boundaries; application programming interface discovery and inventory; threat modeling and mitigations for common application programming interface attacks; and operational practices including audit logging, monitoring, alerting, automated security testing, continuous validation, and strategies for scaling security across many endpoints and services.

EasyTechnical

103 practiced

Explain the core OAuth 2.0 roles (resource owner, client, authorization server, resource server) and the common flows. For each actor below map the role and justify the flow choice:

- mobile app- backend API- third-party web app- end user

Also explain when to use Authorization Code (with PKCE), Client Credentials, and when to avoid the Implicit flow.

MediumTechnical

155 practiced

Describe a secure key management and rotation architecture for API signing and encryption keys. Cover the roles of HSM/KMS vs Vault, envelope encryption, automated rotation schedules, key versioning, secure provisioning to services, access control policies, and rollback strategies if a key is compromised.

MediumSystem Design

74 practiced

You operate a mixed monolith + microservices environment. For security controls (authentication, authorization, rate limiting, input/schema validation, transport security), decide which responsibilities should be enforced at the API gateway/proxy and which should remain inside services. Justify choices with availability, security, and performance trade-offs and propose testing and observability to validate enforcement.

MediumTechnical

157 practiced

Write a Python function verify_jwt(token: str, expected_aud: str, expected_iss: str, jwks_url: str) -> dict that validates a JWT. Requirements: verify signature using JWKS, reject tokens with alg 'none', validate aud/iss/exp/nbf fields, support key rotation by using kid header and caching JWKS with TTL. Pseudocode is acceptable—show the key validation and caching logic.

EasyTechnical

76 practiced

What is API discovery and inventory, and why is it critical for API security? Describe manual and automated approaches (runtime discovery, CI scanning, OpenAPI catalogs), metadata to track (owner, risk, exposure), and how inventory ties into vulnerability scanning and incident response.

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