On 3rd Mar 2021 at 06:26 UTC, our WhatsApp sandbox started to reject 99% of the requests with error code 429. At 07:13 UTC the root cause was identified and the traffic was resumed on 07:17 UTC. Customer may have experienced rejected messages during this time interval.
One customer sending a huge amount of traffic via the WhatsApp sandbox caused it to be overloaded. The account was temporarily suspended and the sandbox came back to normal right thereafter.
We've added a rate limit for the sandbox account to prevent similar issues happening again.