Privacy

Who this is for: developers in their first year or two of writing production code, and the engineers and team leads mentoring them. If you operate the infrastructure rather than write the application, the companion piece is privacy-by-design-server-build. Introduction Most developers learn privacy backwards. They ship a feature; later someone in legal or security flags an issue; later still they retrofit the fix. By that point the data model has been baked in, the API contract is in production, and the rollback is more expensive than the right-thing-to-do would have been on day one. ...

Tested on: Ubuntu 24.04 LTS, Nginx 1.26.x, Apache 2.4.x, PostgreSQL 16.x, Python 3.12. The principles are language- and stack-independent; the recipes are concrete examples. Why this matters Default logging on every component in a typical stack captures more personal data than the operator usually realises. A standard Nginx access log line: 192.0.2.42 - - [17/May/2026:14:01:12 +0000] "GET /search?q=password+reset+for+alice%40example.com HTTP/2.0" 200 4231 "https://example.com/" "Mozilla/5.0 (Macintosh; Intel Mac OS X 14_4) AppleWebKit/605.1.15..." …retains, for as long as the log is kept: ...

Applies to: any new Linux server intended for production where you will store, process, or transit personal data — including the metadata kind (IP addresses, user agents, login timestamps), which counts under GDPR whether or not your application has a “users” table. Why this matters GDPR Article 25 — Data protection by design and by default — is the legal text that turns “we should think about privacy” into “you must demonstrate that you thought about privacy, on paper, before you started processing.” It applies whether or not you have a website with a signup form. An Nginx access log with full client IPs is processing personal data. ...