Change record status: 
Project: 
Introduced in branch: 
11.5.x
Introduced in version: 
11.5.0
Description: 

Using integer values for database connections keys and targets is deprecated.

In fact they were never supported, but strict typehinting introduced in #3532930: Make Drupal\Core\Database\Database type strict and PHPStan L10 compliant surfaced the bug that they might have been passed in without any error.

Impacts: 
Site builders, administrators, editors
Module developers