Field notes — the blog

Notes from inside the system.

Specific write-ups on decisions that moved the needle: architecture trade-offs, delivery pipelines, and leading engineers who are better than you at their part of it.

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The architect's dispatch

One note a month. Nothing else.

A single deep write-up on a system I worked on: the trade-off, the numbers, what I'd do differently.

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Field Notes — Shehzad AslamShort, practical write-ups on architecture, event-driven systems, cloud and DevOps modernization, and engineering leadership.

Connect Claude Code to your database — without handing over the keys — AI, Aug 2026, 17 min. Reusing your app's own role rows is the right instinct, and it still leaves the hard question unanswered: which roles? Hardcode it and the first customer who disagrees files a ticket you cannot close.

Let a model write the tests, let mutation testing grade them — AI, Aug 2026, 16 min. An LLM will happily take you from 44% coverage to 91% in an afternoon, and catch nothing. The fix is not a better prompt — it is a scoring function the model cannot argue with.

Set up an MCP server for your application — AI, Aug 2026, 19 min. Write the server once and every client can use it — Claude Code, your own agent, the Messages API. Tools, resources, transports, config scopes, and the limits that bite in production.

Your first agent with the Claude Agent SDK — AI, Aug 2026, 18 min. Claude Code as a library. Installing it, the two entry points, what the message stream actually contains, and the three limits you set before you let it run.

Custom tools with the Claude Agent SDK — AI, Aug 2026, 16 min. The built-in tools cover files and shell. Everything specific to your business — issue trackers, deploy APIs, internal databases — you supply as an in-process MCP server.

Subagents in the Claude Agent SDK: isolation and parallelism — AI, Aug 2026, 17 min. Delegation buys you a clean context window, real parallelism, and per-agent tool restrictions. It costs you a full context rebuild each time — which is the whole trade.

Hooks and permissions: putting a boundary around an agent — AI, Aug 2026, 19 min. A prompt asking an agent not to do something is a request. A hook that returns deny is a boundary. Blocking, rewriting, auditing, and where each one belongs.

Build a RabbitMQ retry pipeline in Laravel, end to end — Architecture, Aug 2026, 21 min. A complete walkthrough: topology, publisher, consumer contract, delay-exchange backoff, a poison lane, idempotency, and the tests that prove it.

Laravel on ECS Fargate: the whole pipeline, start to finish — Cloud & DevOps, Aug 2026, 19 min. Dockerfile, task definition, secrets, a migration gate, GitHub Actions, health checks that mean something, and a rollback that takes forty seconds.

Make a slow MySQL query fast: a full diagnosis — Cloud & DevOps, Aug 2026, 17 min. One real 4.2-second listing query, taken to 40 milliseconds. Reading EXPLAIN properly, composite index order, covering indexes, and keyset pagination.

Modular monolith in Laravel: enforce the boundaries in CI — Architecture, Aug 2026, 18 min. Independent deploys and clear ownership without a distributed system. Module layout, a contracts-only rule, a failing build when it is broken, and how to extract later.

A Laravel CI pipeline that actually catches things — Cloud & DevOps, Aug 2026, 16 min. Most CI runs tests and stops. Here is the full pipeline: static analysis, real service containers, migration-safety checks, boundary rules, and a nine-minute budget.

Wire an AI reviewer into CI without it becoming noise — AI, Aug 2026, 15 min. The naive version comments on everything and gets muted in a fortnight. Scoping to the diff, structured verdicts, a confidence gate, and measuring the signal ratio.

Context is the job now — AI, Aug 2026, 7 min. The useful work happens before the question. Three minutes of assembling context is the difference between a suggestion I merge and a suggestion I argue with.

Rubber-ducking with something that argues back — AI, Aug 2026, 6 min. I run design decisions past a model before I run them past a person. Not because it is smart — because it is available at 11pm and has no stake in the outcome.

Reading a strange codebase in a day — AI, Aug 2026, 7 min. Inheriting 200k lines used to be a week of grep and optimism. The goal was never to have the code explained — it was to get a map you can be wrong about quickly.

The bottleneck moved to review and nobody staffed for it — Leadership, Aug 2026, 6 min. My team writes considerably more code than it did a year ago and ships about the same amount. The constraint moved, and our process did not move with it.

Why we replaced 14 cron jobs with a single event bus — Architecture, Jul 2026, 8 min. Scheduled jobs are the cheapest way to build a distributed system and the most expensive way to run one. Here is the migration that closed our nightly failure window.

The monolith you should keep — Architecture, Jun 2026, 6 min. Splitting a service is a bet on your ability to run more infrastructure. Often the right architecture decision is a well-bounded module and a boring deploy.

ECS without tears: a deploy pipeline that is genuinely boring — Cloud & DevOps, May 2026, 7 min. Docker build, ECR push, rolling update, health check, done. The interesting part is everything I deliberately left out.

RabbitMQ retries: the three patterns that actually work — Architecture, Apr 2026, 9 min. Naive requeue is an infinite loop with extra steps. Delay exchanges, capped backoff, and a poison lane cover nearly everything you will hit in production.

Reading code as a manager without taking the keyboard — Leadership, Mar 2026, 5 min. Staying technical as an engineering manager is not about writing the tricky patch. It is about reading enough to ask the question that saves a sprint.

Shipping an Android app with an LLM in the loop — AI, Feb 2026, 6 min. Concept to Play Store with AI doing the scaffolding. What it genuinely accelerated, and the two places it quietly cost me a day.

Data modeling for high-volume hiring workloads — Cloud & DevOps, Jan 2026, 8 min. Recruitment traffic is spiky, write-heavy, and read through dashboards. Three modeling choices kept assessment platforms responsive on campaign day.