We build our back-end code with a sever-side language like: Ruby, Node.js, Python, Java, C, PHP, etc. And, for the databases, we could use a relational database, a document-oriented database or a graph database. The definition of the technologies depends on what we are going to develop. Further than the core application logic and the databases, we develop an Application Programming Interface (API), and always perform unit testing. For any of our developments we count with full stack developers.