Not an "engineering blog" in the traditional sense. Percona has been posting deep-dive high-quality pieces about database performance and the inner workings of InnoDB since around 2006, so more than 10 years now. If you've ever had to troubleshoot a weird performance issue in MySQL as an Ops guy or DBA, you've probably ended up finding this in your Google results:
Disclaimer: I am currently employed by Percona, although that is not my motivation for sharing this.