rosneri/writing
field notes — the logVol. 4 · 10 posts · Tel Aviv · updated Mar 2026
$ ls ~/writing --all --sort=recent

Writing

Notes on payments infrastructure, distributed systems, and the startup that didn't make it — plus the dev tools and ~30 books a year that fund the rest. Written down so I don't have to learn it twice.

10 posts
~9 min avg
6topics
LatestEngineeringMar 2026 · 13 min

Deterministic guardrails for AI-written code

A new approach: as an agent writes more of the code, careful review stops scaling. So I encode each standard — strict types, architectural seams, structure caps — as a mechanical check the model can't talk past — enforced at every layer, from the agent's own AI hooks down to CI.

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Mar 2026Systems

Designing a dead-letter queue you can trust

In payments the interesting question isn't what happens when a message processes — it's what happens when it can't. Poison messages, replay safety, per-aggregate ordering, and schema drift, from the financial core at DoorLoop.

11 min read
Jan 2026Systems

Idempotency keys are a design input, not a retry hack

If processing an event twice can't equal processing it once, you don't have a queue — you have a liability. Where the key comes from, and why the check and the effect must commit together.

7 min read
Dec 2025Systems

Stripe Treasury: embedded banking without becoming a bank

What it actually takes to move customer funds — accounts, fund flows, the reconciliation you don't see — and the failure modes that decide the architecture.

9 min read
Nov 2025Startups

SpecBite: an honest postmortem

My failed startup, with the parts I'm not proud of left in. The engineering shipped; the business didn't. Here's the difference, in detail.

14 min read
Nov 2025Books

I keep my reading list in git

~30 books a year, one commit at a time. Queue management, speed, retention, and what I do with the notes when a book is worth keeping.

4 min read
Oct 2025Systems

Running K8s for a side project (don't)

I did it so you can read about it and choose a boring Postgres box on a single VM instead. A breakdown of what the complexity actually bought me.

9 min read
Sep 2025Engineering

DDD for people who actually ship

Domain-driven design without the 500-page book. The three ideas I use every week and the rest I happily ignore.

12 min read
Aug 2025Games

A LitRPG engine in TypeScript

Stats, progression curves, and generated encounters as plain data. Building a narrative game engine I can actually reason about — and test.

7 min read
Jul 2025Dev tools

Building an MCP server in an afternoon

The Model Context Protocol is smaller than it looks. I shipped a working server between lunch and dinner — here's the whole shape of it.

6 min read