Relational databases are among the first systems conceived to manage the storage and access to large bodies of data. They have decades of research and development behind them, and provide very high reliability, efficiency and scalability. Thus, it is a very good idea to rely on them. They are ubiquitous and extremely useful in applications that deal with large volumes of data or in high traffic and high concurrency environments.

The first relational database system I had contact with was Apache Hive, that relies on Apache Hadoop to enable the analysis of very large datasets. I have also used SQLite for personal projects, and later PostgreSQL as SRE for Galaxy. Database skills you can expect from me are writing complex queries, looking into optimizing performance whenever necessary (e.g. building indices, looking at the query plan), caring about details such as isolation levels and designing database schemas. I have not covered the administration of relational databases (e.g. backups, availability, etc).