◢delirium
PAR --:--:--

delirium

Senior Software Engineer · Paris

deliriumSenior Software Engineer · Paris, France · mail [at] proton.me · github.com/nick-delirium · linkedin.com/in/deliriumnick · nick-delirium.github.io

I build the code that records the web, and the player that replays it.

Founding engineer at OpenReplay, the open-source session-replay platform. I own the frontend end to end: tracker, player, browser extension and mobile SDKs. These days I'm also building AI tooling and on-device ML.

  • #2 of 73 contributors to OpenReplay
  • 1.2M npm downloads a month
  • 40–50% cut in pipeline costs
  • 8+ years shipping
Get in touch →

Open to senior frontend & AI engineering roles in Paris

NOW

// oct 2026

At OpenReplay I recently shipped a rewrite of the replay player core, following a rework of the tracker's batch pipeline. Outside work, I build tools for AI coding agents and experiment with on-device ML in JavaScript.

  1. dolly

    open source · 2026 live

    Task memory for AI coding agents, kept as Markdown in the repository: a task board, a log of decisions and versioned specs, so the next session picks up where the last one stopped. Works with Claude Code, opencode and pi, with zero runtime dependencies.

    • TypeScript
    • Claude Code
    • MCP

  2. ██████.js

    in the lab classified

    Contextual search powered by a small Gemma embedding model running in the browser. No server round-trips: the vectors live next to your data. More soon.

    • Gemma
    • embeddings
    • WebGPU / WASM

EXPERIENCE

// 2018 → now

OpenReplay

Senior Software Engineer · R&D · Founding engineer
MAY 2022 → NOWParis · open source

I have full ownership of the frontend: the replay player, the JS and Swift tracker libraries, the Spot Chrome extension and the MCP apps server. I also work directly with enterprise clients every day.

  • Cut the main processing pipeline by 40–50% in space and processing time, saving most enterprise clients hundreds of thousands of USD a year.
  • Rewrote the tracker and player cores. The tracker now uses a versioned binary batch protocol with gzip in a Web Worker; the player core uses shallow observables for CPU efficiency.
  • Made the frontend bundle ~40% smaller and builds 1–2 minutes faster by migrating from webpack 1 to Parcel and Vite.
  • Led the full UI rework of the session replayer while keeping legacy support across enterprise deployments.
  • Shipped offline and conditional recording, feature flags, on-the-fly compression and multi-tab sessions, and moved session heuristics into the browser.
  • Fixed tracker memory leaks. Set up commit linting, AI PR review, per-module coverage and CI/CD from zero. Shipped under HIPAA, GDPR, CCPA and SOC 2.
  • TypeScript
  • React
  • MobX
  • Web Workers
  • Swift
  • React Native
  • Flutter

OpenReplay / deep dive

What changed in the tracker and the player, year by year
  • ~77% of tracker commits
  • ~60% of player commits
  • #2 contributor overall

  1. Split the player into modules and removed Redux and class components from its core (co-led).

  2. Batch compression in the tracker (v7).

  3. Multi-tab sessions over BroadcastChannel. Proxy-based console and network capture.

  4. requestIdleCallback commit scheduling and render-lag detection (v10).

  5. Swift iOS tracker, mobile replayer, React Native connector.

  6. Canvas recording, WebSocket capture, conditional and offline recording, the Spot extension, cross-domain iframes.

  7. In-house CSS selector generator, privateMode, network batcher, product-analytics SDK.

  8. Binary batch V2/V3 (v18), gzip and heuristics in the worker (v19), Flutter SDK, MCP app, player core rewrite.

OZON

Senior Frontend Engineer
SEP 2021 → MAY 20229 moSaint Petersburg

Delivery and warehouse tooling for Russia's largest online marketplace.

  • Co-authored the secure delivery flow with OTP confirmation.
  • Implemented a new warehouse management solution.
  • Worked with UX design to resolve user pain points and streamline the product delivery flow.
  • Completed management and team-lead training.

Fortis

Senior Front-End Engineer
APR 2020 → SEP 20211 yr 6 moSaint Petersburg

Main development company behind monopoly.online, Russia's largest online logistics platform.

  • Built new cargo-tracking, document-management and hauling-auction applications.
  • Implemented a secure document-signing protocol.
  • Co-founded the brand's UI component library.
  • Mentored and onboarded junior developers.

Studybay

Senior Frontend Developer
OCT 2019 → APR 20207 moSaint Petersburg

EdTech platform. Modernized the frontend stack and its build pipeline.

  • Replaced Gulp with a new webpack setup: builds ~300% faster.
  • Ported the legacy Backbone app to React.
  • Redesigned the landing page and core parts of the internal platform.
  • Introduced CI/CD with e2e and unit tests.

Kupibilet

Frontend Developer
JAN 2019 → OCT 201910 moSaint Petersburg

Flight booking. Delivered a full redesign of the user page, ticket booking and billing.

  • Refactored the flight booking flow end to end with redux-saga.
  • Built components for the brand's component library (Storybook).
  • Took part in code review and architecture discussions.

BMSGroup

Frontend Developer
JAN 2018 → JAN 20191 yr 1 moSaint Petersburg

Internal analytics and branding tools, plus an automated site generator.

  • Built internal analytics and branding tools with Vue.js and Node.js.
  • Built a generator that produced a full client brand website on demand from a WhatsApp message.
01 / 07 scroll, use ← → keys, or pick a company

PROJECTS

// side projects · hover to switch the feed

dolly

Git-tracked task memory and planning for AI coding agents. Agents log the work; humans validate it.

2026 · CLIactive

Arctius

A fast, accessible mobile client for Lemmy, the decentralized link aggregator. 33★ on GitHub.

2023–24 · mobilearchived

Notation Quest

Learn chess notation by playing: rebuild real games move by move, or find hidden pieces from the notation.

2026 · PWAlive

bluejay

An open-source Reddit client for Android, built to learn Flutter properly.

2023 · Flutterstudy

Hansang Lab

A mobile app uniting ethnic Koreans in Russia. I led development and releases for iOS and Android and wrote about half the code.

2019–20 · leadnon-profit

████.js

On-device Gemma embeddings for contextual search. Watch this space.

2026 · JSin the lab

STACK

// ls ~/tools
core
  • TypeScript
  • JavaScript
  • Dart
  • Swift
  • Python
  • Go
ui
  • React
  • Vue
  • Svelte
  • MobX
  • Redux
  • redux-saga
  • Zustand
  • Tailwind
  • Styled Components
mobile
  • React Native
  • Expo
  • Flutter
  • iOS (Swift)
browser
  • Web Workers
  • CompressionStream
  • MutationObserver
  • Proxy
  • BroadcastChannel
  • Canvas
  • WebRTC
  • Chrome MV3
tooling
  • Vite
  • Parcel
  • Webpack
  • Bun
  • Jest
  • Cypress
  • ESLint
  • GitHub Actions
  • Linear
server
  • Node
  • Express
  • Koa
  • FastAPI
ai
  • Claude Code
  • OpenAI Codex
  • MCP
  • Ollama
  • Copilot
  • CodeRabbit
  • Greptile
  • on-device embeddings
languages
  • English · professional
  • Russian · native
  • French · elementary

EDUCATION

// degree & recognition

Bachelor's degree, Chemical Engineering

Saint Petersburg State Institute of Technology (Technical University) · 2014–2018

  • Winner · HackUniversity hackathon, track powered by HERE
  • Certified · Triplebyte

My background is in chemical process engineering: systems thinking, measurement and rigour that carry directly into software. I began programming alongside my studies and moved into it professionally in 2018, when a crypto startup brought me in to help build its product.

OFF-DUTY

// hover a line, or a title
  • EVE Onlinefly safe, o7
  • sim racingGT3 and open-wheelers
  • mechanical watches28,800 beats an hour
  • readingDuneNeuromancerThe Lord of the RingsHarry PotterThe WitcherThe IdiotWar and PeaceMasters of RomeEagle of RomeThe InvincibleSolarisDo Androids Dream of Electric Sheep?Akira
  • animeAkiraGundamLegend of the Galactic HeroesFrierenWitch Hat AtelierAttack on TitanMushishi
  • somedaya bee farm

CONTACT

// open channel

An interesting problem, an ambitious team, or just a chat about session replay, AI or EVE? Get in touch.

mailnick.delirium [at] proton.me↗ githubgithub.com/nick-delirium↗ linkedinlinkedin.com/in/deliriumnick↗
© 2026 delirium · Paris no frameworks · no trackers (ironic, I know) · every frame is text