Blog – José Luis Guerrero Zafra
What actually happens between tapping a card and the terminal saying "Approved"
The two-to-three second round trip of a card payment, traced hop by hop: terminal, acquirer, card network, issuer, and back — plus why authorization and settlement are two completely different processes.
Branching strategy: main, pre, and dev
A practical branching model for teams that need a real pre-production gate: main, pre, and short-lived feature branches, with naming conventions and a two-step PR flow.
Migrating a REST service safely: reusing E2E tests to verify external side effects
How to migrate a REST service to a new stack without a regression, by writing the end-to-end test suite once and reusing it both to lock in behavior during the migration and to verify the external services it talks to afterward.
Running old and new in parallel: coexistence during a partial migration
A migration is rarely a single cutover. Here's how to let a partially migrated system and the legacy one it's replacing serve traffic at the same time, safely, until the cutover is actually done.