Database Internals

Preface

Distributed database systems are an integral part of most businesses and the vast majority of software applications. These applications provide logic and a user interface, while database systems take care of data integrity, consistency, and redundancy.

Back in 2000, if you were to choose a database, you would have just a few options, and most of them would be within the realm of relational databases, so differences between them would be relatively small. Of course, this does not mean that all databases were completely the same, but their functionality and use cases were very similar.

Some of these databases have focused on horizontal scaling (scaling out)—improving performance and increasing capacity by running multiple database instances acting as a single logical unit: Gamma Database Machine Project, Teradata, Greenplum, Parallel DB2, and many others. Today, horizontal scaling remains one of the most important properties that customers expect from databases. This can be explained by the rising popularity of cloud-based services. It is often easier to spin up a new instance and add it to the cluster than scaling vertically (scaling up) by moving the database to a larger, more powerful machine. Migrations can be long and painful, potentially incurring downtime.

Around 2010, a new class of eventually consistent databases started appearing, and terms such as NoSQL, and later, big data grew in popularity. Over the last 15 years, the open source community, large internet companies, ...