Developer Practice
The day-to-day craft: regular expressions that match what you meant, test data that behaves like real data, and validation rules that exist for reasons worth knowing. Practical posts about the tools and habits that sit between an idea and working code.
Why Your Regex Doesn't Match: The 7 Most Common Mistakes
A pattern that returns nothing is rarely broken syntax. It is usually one of these seven behaviours doing exactly what you told it to.
How CPF and CNPJ Check Digits Work (With the Algorithm)
A step-by-step walk through the mod-11 arithmetic behind Brazilian document numbers, including the 2026 alphanumeric CNPJ.
UUID v4 vs v7 vs ULID: Which ID Should Your Database Use
Random identifiers are terrible primary keys for reasons that have nothing to do with collisions. Here is what actually goes wrong, and the fix.
How to Generate Realistic Test Data
Need names, emails, and IDs to test your app? Generate realistic fake data locally — no real user records required.
How to Format, Validate, and Compare JSON
A practical guide to cleaning up messy JSON, catching syntax errors, and diffing two payloads — all in the browser.