Look into things like metrics recording and load testers for the language/ide you're using. I.E if C# Api you're building, looking at and recording Application

Look into things like metrics recording and load testers for the language/ide you're using. I.E if C# Api you're building, looking at and recording Application Insight metrics and load testing with something like jMeter would give you an idea of scalability and help you identify bottlenecks, etc.