The article outlines the transaction model of CockroachDB, emphasizing its ability to support ACID transactions across distributed databases without using locks. CockroachDB ensures atomicity, meaning all operations within a transaction are either completed or none are, by implementing a series of steps involving switches and write intents. The transaction process includes creating a transaction record with a unique ID, staging changes using write intents, filtering reads through the transaction's state, committing or aborting transactions, and cleaning up intents to maintain performance. The article notes that CockroachDB also supports concurrent transactions, which will be detailed in a future post. The introductory note mentions that the article was originally written in 2015, and updates are planned to reflect the evolution of CockroachDB since then.