Mohith’s engineering notebook

Notes on building software that holds up.

Technical deep dives on backend systems, infrastructure, performance, and the assumptions that fail in production.

Latest Notes

38 notes

Sep 23, 2026

GPT-6 Sol and Luna Squeezed Out the Middle

Grok, Claude, and GPT releases landed across two days. The telling change in OpenAI's lineup is the missing Terra tier: Sol now costs what Terra used to cost on input, without Terra being retired.

Sep 22, 2026

Claude Opus 5.5 Changed the Price of a Finished Task

At medium effort, Opus 5.5 beats Opus 5 at maximum for about one-fifth of the task cost. The important price is no longer the token. It is the completed job.

Sep 18, 2026

Claude Projects Turned the Folder Into a Coordinator

Claude Projects now directs parallel Claude Code sessions, keeps shared memory, and continues after the laptop closes. Cursor arrived at the same missing layer last week.

Sep 11, 2026

The Missing Layer Between AI Planning and AI Coding

I used one AI chat to think and separate agents to build. Cursor Projects turns the handoffs I managed by hand into the product.

Sep 4, 2026

GPT-6 Astra Is Better Aligned. It Is Also Harder to Watch.

OpenAI's most capable model stays inside the task more often, finds zero-days on its own, and can hide more of the reasoning monitors depend on.

Sep 2, 2026

Anthropic Released One Model Twice. The Difference Is the Guardrails.

Claude Fable 5.1 and Mythos 5.1 share the same intelligence. What changes is who gets access to the dangerous parts.

Browse Series

Earlier Notes

Sep 1, 2026

The Model Learned to Cheat. Then It Learned What the Grader Wanted.

Aug 27, 2026

The Sandbox Had No Internet. The Agents Found One Anyway.

Aug 7, 2026Part 10 · What It Takes to Build a Write-Ahead Log

The Invariants I Didn't Hold

Aug 4, 2026Part 9 · What It Takes to Build a Write-Ahead Log

Testing a Thing Whose Whole Job Is Surviving a Crash

Jul 31, 2026Part 8 · What It Takes to Build a Write-Ahead Log

Checkpoints, and What the Benchmark Wasn't Measuring

Jul 28, 2026Part 7 · What It Takes to Build a Write-Ahead Log

Three Ways to Recover, and What a Torn Tail Costs

Jul 24, 2026Part 6 · What It Takes to Build a Write-Ahead Log

Segments, and the fsync That Hit the Wrong File

Jul 21, 2026Part 5 · What It Takes to Build a Write-Ahead Log

Backpressure, and a Cancel That Doesn't Cancel

Jul 17, 2026Part 4 · What It Takes to Build a Write-Ahead Log

Group Commit, or Refusing to Pay for fsync Alone

Jul 14, 2026Part 3 · What It Takes to Build a Write-Ahead Log

The Sequence Number That Was Never Written Down

Jul 10, 2026Part 2 · What It Takes to Build a Write-Ahead Log

Twenty-Two Bytes in Front of Every Record

Jul 7, 2026Part 1 · What It Takes to Build a Write-Ahead Log

What a Write-Ahead Log Actually Promises

Jul 3, 2026Part 10 · What It Takes to Build a Job Queue

The Reliability Envelope I Didn't Finish

Jun 30, 2026Part 9 · What It Takes to Build a Job Queue

Tracing a Job That Outlives Its Request

Jun 26, 2026Part 8 · What It Takes to Build a Job Queue

The Load Test That Was Supposed to Fail

Jun 23, 2026Part 7 · What It Takes to Build a Job Queue

What 'Processing' Means When the Worker Is Gone

Jun 19, 2026Part 6 · What It Takes to Build a Job Queue

A Timeout Doesn't Stop the Work

Jun 16, 2026Part 5 · What It Takes to Build a Job Queue

Idempotency Is a Race Until the Database Says Otherwise

Jun 12, 2026Part 4 · What It Takes to Build a Job Queue

Retries, Backoff, and Why Jitter Is Not Optional

Jun 9, 2026Part 3 · What It Takes to Build a Job Queue

Three Priority Tiers in One Number

Jun 5, 2026Part 2 · What It Takes to Build a Job Queue

Two Stores, One Job, and the Gap Between Them

Jun 2, 2026Part 1 · What It Takes to Build a Job Queue

Why I Didn't Just Use Celery

May 28, 2026Part 10 · What It Takes to Build a Canvas App

Ten Posts Later: What I'd Do Differently

May 24, 2026Part 9 · What It Takes to Build a Canvas App

Undo Is a Stack of Your Own Mistakes

May 20, 2026Part 8 · What It Takes to Build a Canvas App

The Server Forgets Everything and That's Fine

May 17, 2026Part 7 · What It Takes to Build a Canvas App

What Happens When One Client Can't Keep Up

May 14, 2026Part 6 · What It Takes to Build a Canvas App

Cursors Are Not Part of the Document

May 11, 2026Part 5 · What It Takes to Build a Canvas App

Writing a Binary WebSocket Protocol by Hand

May 8, 2026Part 4 · What It Takes to Build a Canvas App

Real-Time Collaboration Is Not Just Sending Updates

May 5, 2026Part 3 · What It Takes to Build a Canvas App

Why Freehand Drawing Becomes a Bottleneck

May 3, 2026Part 2 · What It Takes to Build a Canvas App

Inside the Rendering Engine of a Canvas App

Apr 30, 2026Part 1 · What It Takes to Build a Canvas App

What Building a Drawing App Taught Me About Performance