Are there any controversial moments when it's unclear whether the problem is with the infrastructure or the code?

Yes, such controversial situations occur quite often. Performance or stability issues can be caused by bugs or inefficiencies in the code, as well as limitations or failures in the infrastructure (servers, network, databases).

To identify the source of the problem, a comprehensive diagnosis is usually conducted:

• Analysis of application logs and metrics (e.g., query execution time, errors).
• Monitoring of infrastructure resources (CPU, memory, disk subsystem, network).
• Comparing behavior in different environments (local, testing, production).
• Using profilers and tracers.

Sometimes the problem manifests only under certain load conditions or configurations, which complicates diagnosis. In such cases, close interaction between development and infrastructure support teams is important for joint troubleshooting and resolution.