When you use the NSX API to manage the networking resources of VMware Cloud Director, there are some limitations to consider.

The NSX API service has three settings that control the rate of incoming API requests.

While it is possible to configure these rate limits using the /api/v1/node/services/http API, it is not recommended. Instead, design your API client to gracefully deal with situations where limits are exceeded.

Per-client rate limit
If a client makes more requests than this limit in one second, the API server refuses to service the request and returns an HTTP 429 Too Many Requests Error. By default, this limit is 100 requests per second.
Per-client concurrency limit
This is the maximum number of outstanding requests that a client can have. For example, a client can open multiple connections to NSX and submit operations on each connection. When this limit is exceeded, the server returns a 429 Too Many Requests error to the client. By default, this limit is 40 concurrent requests.
An overall maximum number of concurrent requests.
This is the maximum number of API requests that can be in process on the server. If the server is at this limit, additional requests are refused and the HTTP error 503 Service Unavailable returns to the client. By default, this limit is 199 concurrent requests.

For details, see the documentation for NSX REST API at VMware {code}.