Most developers use PostgreSQL every day without knowing

what happens under the hood when they run an INSERT. I

wanted to find out. So I built pgstream — a tool that

reads every database change in real time directly from

PostgreSQL's internal log.

What is the WAL?

Every time you insert, update, or delete a row, Postgres

doesn't immediately write to the actual data files. It

first writes the change to a file called the WAL — Write

Ahead Log. This is how Postgres guarantees nothing gets

lost if the server crashes mid-write.

I had read about WAL in docs before but never really

understood why it existed until I started building this.

It clicked when I realized — the WAL is basically a

journal. Postgres writes every intention down first,

then acts on it.

Logical Replication and pgoutput

WAL records are stored in raw binary. You can't just

read them like a text file.…