# ADR 0006. Large Batches via Object Storage + Manifest, Not One Giant HTTP Payload

## Status
Accepted.

Inline batch endpoint in the current spec is `POST /v1/activity-batches`
(spec §37.6), not `POST /v1/event-batches`. Formats (NDJSON, NDJSON.gz,
Parquet, CSV via signed upload + manifest) still stand. There is no
`api/openapi.yaml` in the repository yet; cite spec §37.

## Context
Not every partner supports real-time integration; many will export
periodically (every few minutes to end-of-day). Sending millions of
records as one HTTP JSON payload is expensive and fragile (memory
pressure, timeout risk, poor retry semantics).

## Decision
Small/medium batches may be submitted inline via `POST /v1/event-batches`.
For very large exports: request a signed upload URL, upload compressed
NDJSON/Parquet/CSV directly to S3-compatible object storage, then submit
a manifest referencing that upload for asynchronous processing.

## Consequences
- Batch and real-time paths still converge on the same normalized event
  model post-ingestion (see ADR 0004). This only changes how bytes
  arrive, not how they're processed afterward.
- Requires manifest/checkpoint design and idempotent batch processing
  (same `(source_party_id, source_event_id)` uniqueness as real-time).
- Exact accepted formats are fixed (NDJSON, NDJSON.gz, Parquet, CSV).
  See `api/openapi.yaml`.