SDK customer reported their inline upsert was failing with a 413 from the consumer site. Around 100,000 vectors in one batch, request body around 200 KB. Server saw the request hit the route, never saw the body parse.
express.json() defaults to a 100KB limit on JSON body size. There's a limit option that bumps it. I'd never set it, so I'd silently inherited the 100KB. Inline upserts of more than a couple thousand vectors at typical embedding sizes go over that immediately.
Fix is one line, set limit: '50mb' on the json parser. The interesting bit is how silent the failure was: nothing in the access log indicated a body-size rejection, just the 413, and the SDK's error path mapped 413 to a generic "request too large" that didn't tell the customer what the actual ceiling was. The fix in the SDK is to surface the limit. The fix on the server is to not have a default that small for a write-heavy API in the first place.