TYPO3 Core

TL;DR:

If dropping DB caching as TYPO3 native feature is rejected, then the DB based backend must be recreated.

Depending on how useful the DB cache routine is in the first place, the deprecated Typo3DatabaseBackend may be needed as a PSR-6 compatible solution that works with the new caching framework.

However, several arguments seem to indicate that a "filesystem first" strategy is much more appropriate:

• Historically, DBMS could outperform filesystems quite easily, but this is far from the case these days.
• Having SQL storage on remote servers becomes increasingly popular and performs quite poorly when caches are in DB.
• Overall, keeping the DB connection clear of caching concerns and making it purely about actual data (thus easing things like improving DB performance and monitoring real usage uncluttered by cache usage).
• Filesystem caches can be operated before installation is complete and requires no connections (and can be flushed even if DB connection is broken).
• DB based caches are extremely vulnerable to schema issues and require an initialised schema; any change and the entire application may break.
• And more

So it may be due time to reconsider our use of database caching in the first place. Signs point to either filesystem or third-party services being much more efficient and deployment/development-friendly as cache solutions.