API Design Study Portal

Key takeaways

• Protocol choice follows the caller: REST at the edge for cacheability, gRPC internally, GraphQL for divergent clients.
• Offset pagination both slows down and silently skips or duplicates rows on changing data. Use keyset cursors with a unique tiebreaker.
• Any POST that causes a side effect needs an idempotency key, and the key reservation must be atomic.
• Adding optional fields is safe; changing a field's meaning is the most dangerous change because nothing fails.
• Errors are a contract: stable code, correct status, explicit retryability, correlation ID, no internal detail.