Before
556100k notifications took 45 minutes, and then the run failed.
Laurynas Karvelis · Back-end contractor
Back-ends that keep their cool when traffic explodes.
I'm a senior TypeScript and Node.js engineer. I design and build event-driven AWS systems, queues and data pipelines for teams ranging from startups to The Guardian. I've been shipping software for twenty years.
Now: hybrid contract at The Guardian · fully remote preferred
- 1M in 15 spush notifications, on a pipeline that used to fail at 100k
- £84k / yearcut from one client's AWS bill (£10k down to £3k a month)
- 30 min → <60 sretail shop onboarding, from a manual workflow to fully automated
- 3 productsbuilt solo end to end: one acquired, one live and growing
01 The 15-second story
Same fifteen seconds. Two pipelines.
Pushologies' notification pipeline took 45 minutes to push 100k notifications, then failed. Its largest client, a global football organisation with 7.5M users, needed pushes during live matches. I rebuilt the pipeline from the ground up.
After
1,000,0001M notifications delivered in 15 seconds, sent to full user bases and live segments during matches.
15.0 sYes, this takes fifteen real seconds. So did production.
Each square is 1,000 notifications. The old pipeline is plotted at its average rate before it failed (100k per 45 minutes, about 37 a second). Built on AWS Serverless with multi-stage SQS and Kinesis queueing.
02 Stack
The stack, strictly typed.
Five years of strict TypeScript, nine years of Node.js. Click any type to see the engagements where I shipped it.
type Laurynas = {
languages: | | ;
runtimes: | | ;
frameworks: | "Fastify" | | | | ;
aws: | | | | | | | | | | | "CloudFormation";
databases: | | | | "Redis" | | ;
messaging: "BullMQ" | | | this["aws"];
dataAccess: "Drizzle" | "TypeORM" | | "Mongoose";
validation: | | "OpenAPI";
testing: "bun test" | | | | | | ;
delivery: | "Terraform" | | | ;
protocols: | | | | "gRPC" | ;
edge: | "Caddy" | "NGINX";
security: | "JWT" | ;
os: "Alpine" | | "Arch" | "Ubuntu" | "Amazon Linux" | ;
// "strict": true, always
};
03 Engagements
Twenty years, logged.
Contracting as Explosive Brains Ltd. since 2012: media, adtech, retail, gaming, maritime IoT and government security print.
Showing using
- 2026-07 → now
The Guardiancontract
Senior Full-Stack TypeScript Engineer
Built the internal notification-dispatch back-end that lets journalists push breaking-news newsletters and in-app push notifications in near real time. An Express REST service with Zod-validated ingestion, downstream integrations and extensive unit and end-to-end tests.
- 2023-10 → now
Zero Ad Networkfounder
Sole architect and engineer
A whole distributed ecosystem, built alone: a Chrome and Firefox MV3 extension, NPM and Composer SDKs, a WordPress plugin, Cloudflare Workers and every back-end microservice. Each component is independently designed, tested and shipped through its own CI/CD pipeline. It runs unattended on bare-metal AlmaLinux as plain systemd services, with SQLite holding both the data and the queues: no containers, no database or queue server.
- 2020-03 → 2023-09
Pushologiescontract
Senior Back-End TypeScript Engineer
Rebuilt a failing notification pipeline: from 100k in 45 minutes to 1M in 15 seconds. That unblocked the largest client, a global football organisation with 7.5M users. I designed the whole AWS Serverless platform serving around 20 B2B clients, including a bespoke Cognito mock server for isolated integration testing.
- 2019-03 → 2019-09
NearStcontract
Senior Back-End TypeScript Engineer
Cut monthly AWS spend from £10k to £3k by redesigning the inventory pipeline around Kinesis, SQS and a custom Node.js Streams architecture that survives malformed CSVs. I also automated shop onboarding, taking it from 30 manual minutes to under 60 seconds.
- 2018-04 → 2018-10
90 Percent of Everythingcontract
Senior Back-End JavaScript Engineer
Reverse-engineered an undocumented IoT serial protocol over USB and built the always-on vessel-side service that streams shipping telemetry over satellite links without losing a data point. Then carried it cloud-side through Kafka and Lambda, and shipped a GraphQL-backed B2B app for a second team.
- 2016-10 → 2018-04
Automated trading platformsabbatical
Designer and builder
An algorithmic crypto trading system built from scratch. Its proprietary "zone" algorithm made around 70% of trades profitable. It recovered from failures on its own: RAM exhaustion, exchange API outages, dropped sockets and interrupted orders.
- 2016-04 → 2016-10
Dixons Carphone Warehousecontract
Senior Back-End Node.js Engineer
Built a JSON-Schema-driven recursive validator for arbitrarily nested 1MB+ documents, where naive approaches had failed. Delivered the service end to end with 95% test coverage, set as my own standard rather than the client's.
- 2014-09 → 2015-10
Geektasticco-founder
Full-stack engineer, solo build
A developer assessment and hiring platform with paid peer code review. Grew it to about £10k a month in recurring revenue, and it was acquired.
Earlier: 2003 to 2016
- 2015-11 → 2016-02
Essence Digitalcontract
Senior Front-End JavaScript Engineer
A B2B app for managing multi-million-dollar ad campaigns. I also drove product decisions from requirements through to UX flows.
- 2014-05 → 2014-08
The Press Associationcontract
Senior Front-End Engineer
A complete photo licensing platform covering search, browse and purchase, on a Sails.js back-end. Built a masonry grid years before CSS Grid existed.
- 2014-04 → 2014-05
Signal Noisecontract
Senior Front-End Engineer
A big-data visualisation prototype for EE, rendered on Canvas with Easel.js, running at 60fps on 2014 tablets.
- 2013-06 → 2014-01
Gamesys · Virgin UK Pokercontract
Senior Front-End JavaScript Engineer
One of an 8-person senior team. I owned the whole player-facing meta-game layer (lobby, profile, inventory, progression and rewards) with strict TDD throughout.
- 2012-10 → 2013-07
Bonza Gaming, founded by Unibetcontract
Senior Front-End JavaScript Engineer
Shipped one of the world's first Facebook-approved gambling apps. A Node.js mock back-end let front-end delivery run in parallel with the Java team.
- 2012-03 → 2012-09
De La Rue plccontract
Senior Back-End PHP Engineer
A greenfield integration layer for government clients ordering banknotes and passports. 95% test coverage was mandated, with strict SOAP contracts on both sides.
- 2011-02 → 2012-02
Zugo Services
Full-Stack PHP/JS Engineer
Took a platform serving 10M users a month from specification to launch, and mentored junior engineers along the way.
- 2010-08 → 2011-02
Analytics SEO
Full-Stack PHP Engineer
Rendered charts server-side with early Node.js in a headless DOM, back in 2010. Also tuned a 200GB MySQL database.
- 2003 → 2010
Early career, Lithuania
Full-Stack PHP/JS Engineer
Senior PHP engineer at Laisvalaikio Dovanos. Founded Made By (20+ client sites on a proprietary CMS) and co-founded E-vaizdas.net (CRM, billing and hosting management).
04 How I work
A senior engineer others can lean on.
I own the design
I make system design decisions, set the technical direction that follows from them and stay to see them run in production.
Tests are my discipline
Testing is a discipline I impose on myself, not a checkbox imposed by others. I've built mock back-ends and mock auth servers just to test properly.
The team gets better too
"World-class engineer", in the words of more than one CTO. I bring humour, curiosity and a team-first attitude, and I raise the bar technically while making the team better to be part of.
05 Off the clock
When I'm not on a contract.
Hardware, wood, engines and small Linux boxes: anything I can take apart and put back together better.
- FPV quadcoptersbuild and fly
- Electronicssoldering, prototyping
- Car mechanics & carpentrygarage, workshop
- LinuxAlpine, Arch
- Rock climbing, gym, runningkeeps me sane
- LanguagesLithuanian, English, Portuguese, German, Russian
Contact
Got a system that falls over at scale?
Tell me what's breaking. I'll tell you honestly whether I'm the right person to fix it.
helloexplosive-brains.com