As a developer, you will be seeing numerous articles on Big Data, containers, complex algorithms, caching, etc. But the reality is that a lot of us still have to solve simple problems, especially if one is a freelance programmer or working with small companies.
A simple use case is that of data, coming in spreadsheets or CSV files, have to be visualized in a simple dashboard. You and the customer agree to build it as a web application. There are plentiful ways, from PHP to the Java-based Metabase, of implementing the solution. Since I have experience with Ruby on Rails (RoR or just Rails) and it has extensive easy-to-use libraries, it's my first go-to choice to build a web application real quick.