Read access to the Dynatrace API is free of charge on a fair use model. You're charged for defining and pushing new custom metrics through the Dynatrace API on a per-metric, per-month basis. Refer to DDUs for metrics for detailed information about custom metric ingestion and how this affects your consumption of Dynatrace monitoring.
The payload size is limited to 1 MB. Exceptions are:
Every environment has a limited thread pool (with a queue) for request processing. You reach the limit when both thread pool and its queue are full or the request times out in the queue (timeout is 10 seconds). When you reach the limit, your requests return the response code 429.
This approach enables you to execute a high number of cheap requests without hitting the limit, and it protects your environment from being overloaded by many expensive requests.