Batch LLM APIs: Slash Costs on Background Work

Batch LLM APIs explained: how async batch endpoints cut costs by up to 50%, when to use them, and how to design workloads around them.

LayerFlow Team6 min read
Batch LLM APIs: Slash Costs on Background Work — LayerFlow blog illustration

Batch LLM APIs let you submit a large set of requests that run asynchronously, typically at a 50% discount. For background work — re-scoring, bulk generation, data enrichment — they can cut your bill in half.

What batch means

  • You submit many requests in one job.
  • The provider processes them asynchronously.
  • Results land in hours or a day, not seconds.
  • Cost is usually significantly lower than real-time.

When to use batch

  • Bulk content generation (drafts, meta, summaries).
  • Data enrichment and classification at scale.
  • Re-running evals and scoring.
  • Backfill and re-processing jobs.
  • Anything without a synchronous user waiting.

Designing a batch workflow

  1. Prepare inputs as JSONL files.
  2. Submit the batch job.
  3. Poll for completion or use webhooks.
  4. Download results and map back to inputs.
  5. Handle partial failures and retry only failed rows.

Caveats

  • Latency is hours, not seconds — no interactive use.
  • Different providers have different formats and limits.
  • Quotas may be separate from real-time quotas.
  • Not all models support batch mode.

FAQ

How much does batch API save?+

Most providers discount batch calls by about 50% compared to real-time. Savings depend on provider and workload.

When should I use a batch API?+

When results aren't needed immediately: bulk generation, enrichment, evals, and backfills.

Can I use batch for chat?+

Not for real-time chat — batch runs take hours. Use real-time endpoints for anything interactive.

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