Why Database Snapshot Isolation Is Not Serializable

In this episode, Lucas and Luna unpack the difference between snapshot isolation and true serializability in database transactions. Using the classic write-skew example with a hospital on-call schedule, they explain why snapshot isolation—the default in PostgreSQL and many cloud databases—can violate the guarantees developers assume they're getting. They walk through how PostgreSQL uses SSI (serializable snapshot isolation) to detect dangerous read-write dependencies, and why that comes with a performance cost. They also discuss real-world incidents where write skew led to subtle bugs, and how to think about choosing the right isolation level for your workload. If you've ever wondered why your database didn't prevent a race condition, this episode gives you the mental model to understand it and the vocabulary to talk about it. #SnapshotIsolation #Serializability #DatabaseTransactions #WriteSkew #PostgreSQL #SQLServer #Oracle #MySQL #SSI #IsolationLevels #ACID #ConcurrencyControl #DatabaseInternals #DataEngineering #TechPodcast #FexingoBusiness #BusinessPodcast #DatabaseTech Keep every episode free: buymeacoffee.com/fexingo