Why do my Data Store or NoSQL calls fail with 'Concurrency limit reached for the feature COMPONENT' when many users use my app at once?

This happens when too many requests to a Catalyst CloudScale component, such as Data Store (including ZCQL queries) or NoSQL, run at the same moment. Catalyst returns HTTP 429 TOO_MANY_REQUESTS for the requests above the limit. It can appear even when your functions or AppSail service handle the load, because the component has its own concurrency limit.

1. Send fewer requests at once: combine lookups into one ZCQL query, insert several rows in one insertRows() call, and avoid one query per record inside a loop.
2. Keep values you read often in Catalyst CloudScale Cache instead of querying them each time.
3. Retry refused requests after a short delay that grows with each attempt.
4. If you still need more simultaneous operations, contact Catalyst support with the environment, the component, the error text and time, and your expected peak number of simultaneous operations.

Refer to the Error Codes help page for details.