Working on a big symfony project with a quite common stack (API with APIP, lots of doctrine entities and all config in YAML files), we experienced performances issues in both dev and prod mode.
I took my headband lamp (hi blackfire) and dug. I learned A LOT and discovered quite a few issues that results to a lot of pull requests that got merged.
This talk will be a feedback of the process used and the lessons learned. It will be both practical and theoric.