This is exactly the approach I took. Proxy layer that:
- Uses atomic records (fence tokens) to prevent concurrent execution
- Checks external system first before retrying (the retrieval step)
- Records result for future lookups
The atomic records part is critical - I learned the hard way that just checking a DB flag isn't enough (process can freeze between check and execute, lease expires, another process takes over, both execute).
How do you handle the case where:
1. Process acquires atomic lock
2. Calls external API successfully
3. Process freezes before releasing lock
4. Lock expires, new process acquires it
5. New process calls API again → duplicate
Do you just accept this edge case (rare but possible)? Or is there a mitigation I'm missing?
The atomic records part is critical - I learned the hard way that just checking a DB flag isn't enough (process can freeze between check and execute, lease expires, another process takes over, both execute).
How do you handle the case where: 1. Process acquires atomic lock 2. Calls external API successfully 3. Process freezes before releasing lock 4. Lock expires, new process acquires it 5. New process calls API again → duplicate
Do you just accept this edge case (rare but possible)? Or is there a mitigation I'm missing?