On the Trivago Tech blog they've shared some of their experience in continuous performance improvements in PHP applications and how the Blackfire.io service helped them get their best performance.

Our mission is to provide the user with the ideal hotel at the lowest rate. Our backend consists of several services written in different languages. To succeed at this goal we do complex tasks in our main application developed in PHP. While doing this we need to keep the website as fast as possible.

We started to look for some tool that could help us identify performance issues in our code base. We evaluated Blackfire and decided that it was a good fit for our use case.

The article starts by answering the question of "why Blackfire?" and continues on, showing how they integrated it with their workflow. They use the SaltStack tooling to set up servers and configure them so it was just a matter of integrating the Blackfire agent and probe extension via that. They include an overall diagram of how it fits into the architecture and how they worked around the lack of Bitbucket server support. The post finishes with some examples of performance metrics from before and after the optimizations from their results stored in InfluxDB.