Introduction

1. What This Module Covers

This is the smallest module in the course: four patterns: and the hardest material. Everything before it quietly relied on a guarantee you have been using your whole career without noticing: the single-machine transaction. On one database, "subtract from checking, add to savings" either fully happens or fully does not: the database's write-ahead log provides that all-or-nothing property (the word for it is atomicity) so smoothly you have never had to think about it.

Then the course happened