PostgreSQL

The guiding principle (the motto) Keep UTC for as long as possible. Change to a local timezone only when it is truly required. This principle was not theoretical. It emerged from a real incident — one that almost became a production bug, and only didn’t because of a fortunate configuration coincidence. Why time zones are dangerous in ETL Time-related issues are among the hardest problems in data engineering because: ...

Summary I was generating deterministic UUID v5 primary keys from business keys. It worked well—until subtle but serious collision risks appeared: Ambiguous concatenation (ab + cd vs a + bcd) Cross-table collisions (different tables, same business values → same UUID) This post presents a clean, modular solution using explicit separators and namespace scoping, and explores the harder problem of multi-source ingestion. ⚙️ Context & Problem In data platforms and ETL systems, business keys are often the only stable identifiers available (for example, composite natural keys). To ensure idempotency and simplify upserts and deduplication, a common pattern is: ...

Resumo: Indexes are one of the first performance tools every PostgreSQL user learns — and one of the easiest ways to accidentally slow a system down. This article explains how indexes actually work, why they are never free, how different index types behave in real workloads, and how fillfactor quietly determines whether your database ages gracefully or slowly collapses under write pressure. Indexes Feel Like Magic (At First) You run a query on a table with millions of rows. ...

Summary: ORMs make development faster, but mastering SQL and database internals turns good backend engineers into great ones. Here’s why understanding both levels — abstraction and reality — matters. ⚙️ Context & Problem Modern web frameworks — Django, FastAPI, Spring Boot, Laravel — all encourage the use of Object-Relational Mappers (ORMs). They make it easy to map objects to tables, run queries in a few lines of code, and forget about SQL altogether. ...