Data System Design Explained to My Wife: ACID Transactions

Sun, 09 Mar 2025 16:16:44 +0000

Why transactions exist

“In the harsh reality of data systems, many things can go wrong:

The database software or hardware may fail at any moment (including in the middle of a write operation).

The application may crash at any moment (including in the middle of a series of operations).

Network interruptions may unexpectedly cut the connection between the database and the application, or between databases.

Multiple clients may write to the database at the same time, overwriting each other’s changes.

A client may read nonsensical data because the data was only partially updated.

Race conditions between clients may cause surprising errors.” — Designing Data-Intensive Applications

In concurrent programming, we often care about the correctness of multiple threads/processes/coroutines modifying the same block of memory, and we solve this with atomic variables and locks to implement critical sections. In real life and in development, however, it’s more often the case that an actor completes a task through a series of operations, and here too we want something like an atomic variable to protect that series of operations, preventing unexpected situations when multiple actors operate at once.

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Data System Design Explained to My Wife: ACID Transactions

Why transactions exist