Refactoring.Guru makes it easy for you to discover everything you need to know about refactoring, design patterns, SOLID principles, and other smart programming topics.

https://refactoring.guru/

Online Regular Expression Evaluator:https://regex101.com/

Free Online Formatters: https://www.freeformatter.com/xml-formatter.html

https://microservices.io/index.html

Modules and Microservices

• Modules vs. microservices

• In Defence of the Monolith, Part 1
• In Defence of the Monolith, Part 1

Reactive Programming

• Notes on Reactive Programming Part I: The Reactive Landscape
• Reactor: A Foundation for Asynchronous Applications on the JVM
• Reactor by Example

Misc

• Latency Numbers Every Programmer Should Know