The per-second limit is the more immediate constraint developers face. It operates on a sliding window—a common industry practice—rather than a rigid, calendar-based second. This means that making 10 requests at millisecond 0 and another request at millisecond 500 of the same second would trigger a 429 Too Many Requests HTTP status code for the 11th attempt. Lexoffice returns this error along with a Retry-After header, suggesting how many seconds to wait before resuming.
The (by Lexware) enforces a strict rate limit to maintain system stability and performance for all users. Key Rate Limit Specifications lexoffice api rate limit
Financial data changes relatively infrequently for many use cases. Implement caching for read-heavy endpoints like contact lists or tax types. A cache TTL (time-to-live) of 5–15 minutes can eliminate the need to query the same data repeatedly during a single user session. The per-second limit is the more immediate constraint
Mitigates the risk of Denial of Service (DoS) attacks. Lexoffice returns this error along with a Retry-After
If you exceed the limit, the API returns an HTTP 429 (Too Many Requests) status code, and the request is not processed. Best Practices for Developers
Develop and test your integration using free Lexware Test-Accounts (valid for 30 days) before going live. Lexware API Documentation