Idempotency Strategy: Database-Level Keys vs. Edge Function Routing

Preventing Duplicate Writes During Execution Retries

Vercel Serverless Functions may execute multiple times for a single request due to platform-level retries or cold start timeouts. Because the runtime does not natively manage idempotency, write operations to external databases risk duplication if a function is retried after a partial success.

There is a design trade-off between implementing idempotency keys within the database layer using Serverless Functions or utilizing Edge Functions to handle request routing and validation before hitting a write-heavy endpoint.

While Serverless Functions offer the full Node.js API for complex database transactions, Edge Functions provide lower latency but operate under stricter runtime constraints and memory limits.

• Serverless approach: Higher resource limits but requires manual idempotency logic in the persistence layer.
• Edge approach: Faster request filtering but limited by a restricted runtime API.

Which approach is more sustainable for high-throughput write operations where strict "exactly-once" semantics are required? How do the execution limits of Edge Functions impact the ability to verify idempotency keys before triggering a Serverless write?