Application Programming Interface Design and Communication Questions

Test the candidates ability to design clean application programming interfaces that are intuitive for clients and to clearly explain the design and its trade offs. Coverage includes resource and contract design, request and response formats, error handling and status conventions, versioning and backward compatibility, performance considerations, rate limiting and security basics, and selection of synchronous versus asynchronous communication approaches. At senior levels this expands to event driven patterns, message based systems, gateway patterns, and how interface decisions affect downstream systems and reliability.

MediumTechnical

0 practiced

Design a cursor-based pagination scheme for a feed API where new items are frequently inserted. Explain how you would generate stable cursors, ensure monotonic ordering across pages, handle items deleted between requests, and design the response metadata (next cursor, prev cursor, approximate totals).

HardTechnical

0 practiced

Design an observability and tracing strategy that propagates request context and trace identifiers across HTTP APIs and asynchronous message queues. Include choices for headers (traceparent/trace-id), correlation IDs, sampling strategy, log enrichment, span tagging conventions, and how to visualize distributed traces for debugging latency spikes.

EasyTechnical

0 practiced

Explain the token bucket algorithm for rate limiting. Describe how tokens are refilled, consumed, and how the bucket size and refill rate determine steady-state throughput and burst capacity. Give a numeric example for enforcing 100 requests per minute with a burst capacity of 20.

HardSystem Design

0 practiced

Architect an API gateway component that must perform authentication, enforce per-client rate limits, orchestrate retries to downstream services with circuit breakers, and translate incoming GraphQL requests into REST backend calls. Provide component layout, data flows, failure isolation techniques, and considerations to avoid making the gateway a single point of failure.

EasyTechnical

0 practiced

List and explain the appropriate HTTP status codes for these API outcomes and justify your choices: successful resource creation, validation error with field details, unauthorized access, forbidden action, resource not found, rate limit exceeded, and internal server error. For each, give numeric code and short rationale.

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