LINE error 429: Too Many Requests (concurrent audience operations)

This is the third documented meaning of 429 on the Messaging API: not request rate, not monthly quota, but parallelism. The reference sets "a limit on the number of concurrent endpoint operations per audience ID (audienceGroupId), for creating an audience for uploading user IDs and adding user IDs to an audience" - the four upload-audience endpoints (create by JSON, create by file, add by JSON, add by file) share a combined maximum of 10 concurrent operations. Cross it and: "Requests that exceed the limit on the number of concurrent operations will return an error with status code 429 Too Many Requests. If you've received an error, wait a while before making a request again."

Concurrency here is measured by job state, not by open HTTP connections. Audience uploads are processed asynchronously; the docs tell you to count jobs via the get-audience-data endpoint: "if the status of a job (jobs[].jobStatus property) is waiting to run (QUEUED) or running (WORKING), it will be counted as an operation." So a burst of add-user-IDs calls can trip the limit even if each HTTP request returned quickly - the queued jobs are still "operations" until they finish.

Distinguish this from the sibling 429s by context: it occurs on audience-management endpoints during bulk segment builds, while the rate-limit 429 is about request frequency anywhere and the monthly-limit 429 carries its own message string. Audience endpoints additionally have a 60-requests-per-minute rate limit, so aggressive uploaders can hit either ceiling.

HTTP/1.1 429 Too Many Requests

// Returned when more than 10 audience upload/update operations
// are QUEUED or WORKING at the same time. Wait, then retry.

Model audience building as a queue with completion tracking, not fire-and-forget: submit, poll jobs[].jobStatus, then submit the next chunk. Prefer the file-based endpoints for bulk loads so one job replaces many, and keep the 60-requests-per-minute endpoint budget in mind for the surrounding calls. See audience limits for the full set of caps.