At Least Once

Writing

Backend systems, taken apart. Plus the questions that outlast a workday.

Featured

Build an OAuth2 Authorization Server with Spring Boot
Series15 parts66 min

Build an OAuth2 Authorization Server

Fourteen parts, from an empty Spring Boot project to a production-oriented OAuth 2.1-style and OpenID Connect authorization server: PKCE, JWT, refresh rotation, PostgreSQL, user and client administration, revocation, Docker and CI.

  • oauth2
  • oidc
  • spring-boot
  • pkce
  1. 00The planabout 10 minutes, reading only
  2. 01The mental modelabout 25 minutes, reading only
  3. 02A server that startsabout 45 minutes
  4. 03Authorization Code and PKCE, by handabout 40 minutes

and 11 more

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Featured

Build Redis From Scratch with Java
Series14 parts158 min

Build Redis From Scratch

Thirteen parts, from an empty Maven project to a server that speaks RESP, persists to disk, and replicates to a second instance, plus a reference of every link they lean on. Java, no libraries.

  • java
  • maven
  • setup
  • sockets
  1. 00Getting set upabout 30 minutes, mostly downloads
  2. 01TCP before Redisabout 45 minutes
  3. 02One read is not one requestabout 40 minutes
  4. 03What redis-cli actually sendsabout 60 minutes

and 10 more

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All categories

A desk at night under a wall of notes, a tangle of scribbles overhead
Philosophy4 min

Why Do We Exist in This World?

A raw reflection on purpose, responsibility, and why living in the present matters more than chasing an endless future.

  • purpose
  • life
A fountain pen on a page headed Why I Write, beside an open notebook
Life4 min

Why I Write

I write because it helps me understand systems, life, responsibility, and myself. This is the manifesto behind this space.

  • writing
  • engineering