Over the last two decades as a consultant, I visited several government institutions, banks, and financial institutions, establishing a common factor for a lack of performance in applications that are working in production, and I found common issues that can be avoided if you use a set of good practices as part of your SDLC.
It's important to pay close attention to performance, because it brings huge trouble to companies, project sponsors, and customers since an application that faces this problem brings dissatisfaction on several levels.
Before giving recommendations, we are going to review and understand the non-functional requirements of scalability, availability, and performance.