We have tried and compared several tools and came back to Scout because it's the best mix of usability/learning curve and functionalities

I used Scout APM to diagnose slow endpoints. It shows queries and how long each of them took. which helps finding bottlenecks. It is very UI friendly and shows the exact lines of code for where things took place. It also shows response time and throughput graph for each endpoint to easily spot if there is anything that is out of ordinary. Also, It shows metrics across all the transaction for each endpoint which is very helpful (Shows average total time for each transactions and the percentage of the time consumed for that endpoint). In addition to identifying or diagnose slow endpoints. It is very useful tool to diagnose the presence of N + 1 queries. It has n + 1 insight which analyzes the application for N + 1 queries consuming over 150 ms. This also brings you to exact line of code where it is happening (with backtraces) and also shows the sql query for the backtrace.

The ability to see a snapshot of memory growth, request times, and requests per second all in one place. It's super easy to use and see the timings for each section.