API Integration and System Connectivity Questions

Covers the end to end concepts and practices for connecting systems using application programming interfaces and integration middleware. Candidates should understand REST and HTTP fundamentals, webhooks versus polling, API authentication and authorization patterns, request and response formats, rate limiting, versioning, and reading API documentation. Include practical skills for building and troubleshooting integrations: data mapping and transformation, schema mapping, message formats, error handling and retry strategies, idempotency, logging and monitoring, and ensuring data consistency across synchronous and asynchronous flows. Also includes integration tooling and middleware platforms, real time versus batch synchronization, designing for partial failures and back pressure, and frontend concerns such as async data fetching, loading and error states, pagination, optimistic updates, and race condition mitigation.

MediumTechnical

87 practiced

In Node.js (pseudocode acceptable), implement webhook signature verification using HMAC-SHA256. Requirements: validate the 'X-Signature' header against body and a shared secret, reject requests with invalid signatures, and accept requests only if the timestamp header is within ±5 minutes to mitigate replay attacks.

MediumTechnical

92 practiced

Compare offset-based pagination and cursor-based pagination. For a dataset with high churn and very large pages, explain performance, stability, and correctness trade-offs. Provide an example response shape for cursor-based pagination containing 'next_cursor' and 'has_more'.

MediumTechnical

89 practiced

On a single-page application, design optimistic UI updates for a 'like' action that calls an API. Discuss how to show pending state, rollback on server rejection, merge conflicts when server state differs, multi-tab synchronization, and metrics to evaluate UX correctness.

HardTechnical

74 practiced

Design a back-pressure management strategy for a pipeline that begins at an API gateway, passes through a worker pool, and calls third-party endpoints. Include queue sizing, admission control (dropping vs throttling), circuit breakers, dynamic scaling, and observability to detect and respond to overload. Explain how you'd avoid cascading failures.

HardSystem Design

96 practiced

Design a system to enforce per-tenant rate limits and quotas in a multi-tenant API stack while preventing noisy-neighbor effects and enabling predictable billing. Explain enforcement points, quota storage, throttling vs queuing decisions, and architectural choices to shard or partition tenant state.

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