In some possible cases, the APIM Gateway DB might be down for any reason.
During the downt-time (short or long) - would my Gateway still be responsive to requests?
If we stop the APIM Gateway MySQL DB - would be still be able to process and serve requests coming to this Gateway?
As long as the Gateway is not updating it's DB for Auditing or Policy changes and as long as the requested services also does not require any of the Gateway DB operation, that service will be active and honor the requests such as HTTP Route.
It will vary from Gateway host to another the amount of time it will be up like this.
We have seen cases from 10 min to 40 min and this is normal.