As you may know, as with any public API, the Xray GraphQL API protects against excessive or abusive calls to Xray Cloud's servers.
Currently, the limit is 60 calls per minute. This limit is applied to each Jira instance, so for example, if you have another user making requests in parallel, this limit has to be divided between these 2 users.
So, imagine: if you are updating Tests not to reach this limit, an idea to resolve this issue would be introducing a timer and then counting the number of requests; when closer to 60 calls/mutations, you can put a Sleep (few seconds) and then continue the iteration to update Tests.
Additionally, each GraphQL request supports 25 resolvers so that you can update 25 Tests in just one request. Please see more info here.
Related articles
https://xray.cloud.getxray.app/doc/graphql/