How would you approach debugging a complex issue in a production environment?

In my first job as a junior developer, I was part of a team responsible for maintaining a critical client application. One day, we noticed that users were experiencing significant delays when accessing the system. I took the initiative to investigate the issue. I started by checking the server logs and quickly discovered that a recent code deployment had introduced inefficiencies. I worked with the senior developers to roll back the changes and simultaneously began optimizing the code. We managed to resolve the issue within hours, minimizing downtime. This experience highlighted the importance of quick problem-solving and effective team collaboration in a production environment.