What points to pay attention to when hosting a yii2 project on heroku?

Question

Heroku

What points to pay attention to when hosting a yii2 project on heroku?
Now the following services are working, and done:
1) Mailgun for sending email
2) MemCachier Memcached, additional user sessions hang on it.
3) user files are stored on s3.
4) Dyno is up from heroku-php-nginx
What else is worth looking at? What to do with the assets section? leave as is?
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Sub-question - are there any ways to debug an error on heroku?
And understand the error in the application or in the server settings? Unstable 502 arrives, and on different controllers, and in different actions.
Support says the problem is on our end. It doesn't get to the script execution.

For example, one request returns 502, and the next one in less than a second on the same controller returns a normal response. Caching is disabled, the request contains a simple request to the database with pre-authorization.

at=info method=POST path="{path}" host={server} request_id=3d81f000-0964-410f-8bef-1fc4452f4d1a fwd="{ip}" dyno=web.1 connect=0ms service=15ms status=502 bytes=713 protocol=https

at=info method=POST path="{path}" host={server} request_id=da6b962e-9f83-4b71-a6c4-add094feb0ef fwd="{ip}" dyno=web.1 connect=1ms service=43ms status=200 bytes=7293 protocol=https

Answer 1

For 12 factors .