Vercel Queues hidden message size limit issues

(edited)

Problem

We are trying to use Vercel Queues to process Klaviyo events for analytics purposes. I noticed that when I send messages above ~250 kb they fail with a generic error. We’ve split messages to stay under this undocumented constraint, but that adds rate limit pressure.

Current Behavior

Messages > 250 kb fail with a generic error.
The volume is such that we run up against rate limits often due to message splitting.
The documentation states messages can be up to 100 mb
New messages have higher priority than retry messages, causing delays for retries during high traffic.

Expected Behavior

Support for larger message sizes as documented (up to 100 mb).

Recommendation

A setting to change the behavior to prioritize old messages

Environment

Package: @vercel/queue
Version: 0.1.4

Vercel Alum

For the size limit issue:

Can you share the exact error message you’re receiving when messages fail?
Are you seeing any specific error codes or just generic failures?
Have you tried gradually increasing message size to find the exact threshold?

InternalServerError: {"error":"Failed to store message payload"}

I didn’t find the exact threshold but comparing the ones that succeeded vs the ones that failed it happens between 240 kb and 260 kb which is reminiscient of SQS’s 256 kb limit. Since chunking at 240 kb we have had no issues sending messages.

Update:

At about Apr 06 10:33:19.67GMT the most common error changed from

Queue callback error: Error: Failed to receive/acknowledge message by ID: 429 Too Many Requests at throwCommonHttpError (file:///var/task/node_modules/@vercel/queue/dist/index.mjs:1426:9) at _ApiClient.receiveMessageById (file:///var/task/node_modules/@vercel/queue/dist/index.mjs:1793:7) at process.processTicksAndRejections (node:internal/process/task_queues:95:5) at async ConsumerGroup.consume (file:///var/task/node_modules/@vercel/queue/dist/index.mjs:432:24) at async handleCallback (file:///var/task/node_modules/@vercel/queue/dist/index.mjs:707:5) at async file:///var/task/node_modules/@vercel/queue/dist/index.mjs:2045:9

Queue callback error: MultipartParseError: Unexpected end of stream at StreamingMultipartParser.startProducer (file:///var/task/node_modules/mixpart/dist/index.mjs:207:19) at process.processTicksAndRejections (node:internal/process/task_queues:95:5)

I preferred the 429 error message. The new one makes me feel like there’s something unexpected going on. These messages generally succeed on the next retry.

I was told in a support ticket the file size issue is fixed. I tried removing the chunking logic in a preview deployment and got the exact same behavior. Messages over 256kb fail to send. Same error message as before.

Screenshot 2026-04-22 at 11.35.09 AM

Screenshot 2026-04-22 at 11.39.34 AM

Screenshot 2026-04-22 at 11.40.06 AM

The screenshots above show that the limit is between 254 and 257 kb. I'm convinced the limit is 256kb just like SQS. Do I need to upgrade the vercel/queue sdk? We are currently on 0.1.4. According to Mary the issue was resolved March 28 which was before the 0.1.5 release.