Parallel Requests

Benched.ai Editorial Team

Parallel requests send multiple inference calls concurrently to increase throughput or route around tail latency.

Patterns

Pattern	Description	Best For
Batch fan-out	Same prompt to N models	Ensemble voting
Shard fan-out	Split large prompt into chunks	Parallel summarization
Hedge request	Send duplicate after T ms	Tail mitigation

Concurrency Limits

Resource	Safe Limit
HTTP/2 streams per host	100
OpenAI completions per key	3 000/min
GPU streams (vLLM)	256

Design Trade-offs

Increases cost if duplicates not canceled.
Too many parallel calls hit provider rate limits.
Concurrency bugs cause race conditions in chat state.

Implementation Tips

Use async/await and connection pooling.
Cancel hedged request once first response returns.
Back-off and jitter retries.