How to Prevent Duplicate Writes When Feature Flags Trigger Rollout Toggle Retries

When feature flag retries hit rollout toggle endpoints, they risk creating duplicate writes unless the backend enforces idempotency through durable receipts. The recommended approach binds a single caller-generated key to one operation, committing the receipt and state change together in a single transaction to eliminate gaps between the two. If a retry arrives with the same key and matching data digest, the backend returns the stored result instead of repeating the write. Three key failure scenarios must be tested: lost responses after commit, concurrent worker races, and flag decisions that change between retry attempts. Observability should track logical operations separately from raw request volume, since rising retry traffic can mask a flat committed-operation count and lead to unexpected costs.