We hope that you enjoyed this book and learned how to make your web applications well-performing and easy to maintain, particularly when you use C#, ASP.NET Core, and .NET Core. We tried to keep as much advice as possible applicable to general web app development, while gently introducing you to the latest open source frameworks from Microsoft and others.
Clearly, a topic such as this changes quite rapidly, so keep your eyes open online for updates. Hopefully, a lot of the lessons in this book are generally good ideas and they will still be sensible for a long time to come.
Always keep in mind that optimizing for its own sake is pointless, unless it's literally an academic exercise. You need to measure and weigh the benefits against the downsides; otherwise, you may end up making things worse. It is easy to make things more complex, harder to understand, difficult to maintain, or all of these.
It's important to instill these pragmatic performance ideas into the team culture, or else...