I think it depends on your needs and software, how much time you want to invest, what you want to monitor, do you want to maintain it or you want saas? You wan

I think it depends on your needs and software, how much time you want to invest, what you want to monitor, do you want to maintain it or you want saas? You want metrics from counters you build in your app? (see statsd?) You want to aggregate and do analysis on logs? (see ELK stack?) You want to monitor cloud infrastructure (see stackdriver?) You want to run end to end tests on your application to ensure it's behaving? (see runscope?) As your application grows, you probably want a blend of tools to see inside your app.