Here are possible (non-abusive) reasons why Mastodon is destroying your GS server, in descending order of how you could ameliorate the problem.

0. you're using an incredibly small VM size
1. you're not designating enough php-fpm threads to service incoming pushes
2. you're using opportunisticqm and your load now requires running the queue daemons
3. you're using the mysql queue and you should switch to redis queue or STOMP
4. you're not running enough processes for the queue daemons
5. your hardware is not powerful enough