Development team to support and refine the engine

Question

Highload

Hi all!

The problem is this: there was a development team that developed the engine (PHP + MySQL) from scratch. Which now runs several sites. Over time and with the crisis, the team broke up.
Now there is an acute issue of supporting the code and its refinement for various new projects, as well as optimizing it for highload.
Many teams with whom we managed to communicate offer, as always, to rewrite everything anew, but this option is not considered, for a number of reasons. In particular, I strongly doubt that it is possible to implement the existing functionality in a reasonable time.
Can you recommend any competent, proven development teams? Or companies that can take on a similar project?

Thank you!