Seven Databases in Seven Weeks, 2nd Edition

Appendix 2The CAP Theorem

Understanding the five database genres is important when deciding on which database to use in a particular case, but there’s one other major thing that you should always bear in mind. A recurring theme in this book has been the CAP theorem, which lays bare an unsettling truth about how distributed database systems behave in the face of network instability.

CAP proves that you can create a distributed database that can have one or more of the following qualities: It can be consistent (writes are atomic and all subsequent requests retrieve the new value), available (the database will always return a value as long as a single server is running), and/or partition tolerant (the system will still function even if server ...