I don't want to start a flame war here, but IMO it is a mistake to jump straight to distributed databases (and 90% of the content below is distributed databases) without first learning fundamentals on single node databases. Here's my 10 things to understand about databases: 1. Relational model. Primary keys, foreign keys, normal form. 2. SQL language. Ideally with advanced SQL (CTE, analytics) 3. ACID and how transactions work 4. Write-ahead log (or binlog) and how it is used. Especially around restarts, recovery and replication. 5. Buffer cache, disk storage layout and how they interact 6. What happens when databases start? when they shut down? 7. Indexes, cluster tables, partitions and other types of database structures. 8. Query parsing, planning and optimizing. 9. MVCC and how to deal with its quirks in your DB of choice 10. Security - authentication, authorization, encryption on wire and at rest. 11. (Bonus) Investigating performance issues and making sense of benchmarks. Entire world, stuff that 99% of developers use daily. You can be a deep expert without ever looking at distributed databases. And this also serves as strong foundation once you do. And if you use Postgres, I found this free book super helpful in making sense of things: interdb.jp/pg/