Yannis Kolovos - Senior Backend Engineer

// 01 — work

Experience

VODA.ai

Senior Backend Engineer

ISO/IEC 27001:2022

Sep 2026 – now · Remote

Event-driven backend for AI decision-support software used by municipal water utilities.

Moved synchronous workloads to a parallel, event-driven architecture with AWS SQS, event source mappings and Lambda.
Built high-throughput microservices on PostgreSQL and MongoDB in TypeScript, working across a polyglot codebase with Python and Go, using AI-assisted development.
Added background workers, WebSockets and end-to-end distributed tracing.
Built tooling that runs the full cloud stack on localhost (Docker, AWS, SQS, Lambda).

PythonGoTypeScriptAWS LambdaSQSPostgreSQLMongoDB

Advocate Technologies

Lead Backend Engineer · Founding Engineer

ISO/IEC 27001:2022SOC 2 Type II

Sep 2020 – Jan 2024 · New York · Remote

First employee. Designed the core platform for insurance compliance, a complex and regulated domain. The platform processed $1.5T in loan value.

Designed and ran the core AWS infrastructure, with deployments on Docker.
Built the core GraphQL API (Node.js, Apollo Server, MongoDB) with ACLs and field-level permissions.
Led and mentored a team of 3 engineers, and interviewed and hired new engineers.
Built a queue system (BullMQ, Redis), Redis caching, a rule-driven dynamic fields engine and Stripe payments.

Node.jsGraphQLApolloMongoDBRedisAWSDocker

Primary Colors

Lead Backend Engineer

Sep 2019 – Jun 2022 · New York · Remote

Led backend work for client platforms in retail, tailoring and travel.

Hair Cuttery: −75% request time by moving the legacy REST API to GraphQL. Joined many external APIs into one endpoint with Apollo Federation.
Hemster: built a 50+ model domain (orders, invoicing, payments, alterations, shipping) and a dynamic pricing system. −15% code complexity with a reusable query filter.
Dorsia (AI travel platform): −80% Google Maps API cost through caching. Geospatial search with Elasticsearch, load balancing and auto scaling on AWS.

Ruby on RailsGraphQLPostgreSQLElasticsearchRedisAWS

Earlier

Nimber

Moved core technology from outsourced to in-house, built the backend team, and built the Stripe marketplace (charges, refunds, user verification).

Bosch · Loud & Clear

Lead Developer, end to end, for the MVP of a social-media crisis simulator that trains teams to handle a crisis.

Sensis · Netfira

eCommerce and accounting integrations. Built Active Resource style gems with ORM, using TDD.

Symantec

Built microsites for Symantec's Australasia & Pacific marketing campaigns. They got strong open and conversion rates, and other Symantec regions used them as examples.

// 02 — signal

Recommendations

What people I worked with say about my work.

Yannis is one of the most talented software engineers I've ever worked with. His ability to tackle complex problems with simple, efficient solutions is unmatched. The quality of his code is always clean and a pleasure to read. His unique mix of technical leadership, business-oriented thinking, and experience makes him stand out. Beyond his technical expertise, Yannis is a thoughtful and collaborative teammate who elevates everyone around him. Any team would be fortunate to have him!

Andrew Kordampalos

Zapier AI Growth

Yannis is a true coding maestro, and I've learned an immense amount from his innovative approach to crafting generic code. What truly sets Yannis apart is his exceptional ability to foresee and address edge cases, making our company's API not only robust but bug-free — a rare feat in my professional experience. His dedication to the team and fellow developers is commendable. His exceptional skills, dedication, and inspiring leadership make him an asset to any team.

Ram Sankhavaram

IKEA Software Engineer

Yannis is an enthusiastic, well-travelled developer, with good attention to detail, and a well-rounded coding style. In the months he worked on my team, I found him to be open and collaborative, and was impressed by his rigorous commenting, refactoring, and sense of how things 'should' be done. He was never too bogged down in functionality to remember the important, little things, which is refreshing in programmers of his calibre.

Neil Pearson

Atlassian Senior Software Engineer

→ Read all 7 recommendations on LinkedIn

// 04 — writing

Articles

Articles I've written on backend engineering, GraphQL and AI.

Building a PDF Chat System with RAG: A Step-by-Step Implementation Guide

A practical guide to implementing Retrieval-Augmented Generation with local LLMs and vector search.

JsonLogic + GraphQL Unsupported Query Keys

A json-logic-js-graphql and Lodash to handle unsupported JSONLogic operators in GraphQL queries, providing flexibility and seamless integration for rule validation and data manipulation.

Keep your codebase clean with Rails API and GraphQL Connection Helpers

Creating reusable helpers for GraphQL connections in a Rails API, covering ordering, filtering by datetime fields, search integration, and adding total counts to ensure a clean, scalable, and elegant codebase.

→ More articles on Medium

// 05 — open source

Open Source

In my free time, I strive to create and contribute to open-source projects. Here are some of the projects I've worked on:

docuGraphRAG.js knowledge graph of entities extracted from a CV

→ More projects on GitHub

// 06 — community

Volunteering

I always strive to contribute and make a difference whenever I can. Here are a few moments.

Hacker: ElevenLabs x a16z Worldwide Hackathon: Built Kip.AI, an innovative AI chat agent using Google Gemini API and ElevenLabs voice API
Mentor: StCatsHacks Hackathon: St. Catherine's British School is the first inter-school hackathon held in Athens, Greece
Mentor: Startup Hackathon Melbourne: "Startup Hackathon" will bring together teams of entrepreneurial IT and design students from universities around Victoria
Hacker: RedKite Hack to Help: a hackathon seeking Melbourne's digital entrepreneurs to build a platform to leverage a national campaign (YBF Ventures)
Hacker: Startup Hackathon: Melbourne (Inspire9)
Volunteer: Melbourne Community Toy Library: Develop the new layout of Melbourne Community Toy Library

// 07 — recognition

Honors & Awards

Here are some notable honors and awards for projects I've had the privilege to be a part of.

Best Use of Technology for Learning: (Loud & Clear) Australian Institute of Training and Development
Startup Hackathon, Melbourne: Student Entrepreneurs inc.
Verification and validation for on-line transactions: (University Thesis) Public Institution Of Higher Education Western Greece
Master the Mainframe: RMIT University / IBM

// 08 — foundation

Education

Learning and building a strong foundation for my professional journey.

M.Sc Master of Computing, Software Engineering

RMIT University

B.Sc School Of Economics, Business Administration

Public Institution Of Higher Education Western Greece

Thesis: "Verification and validation for online transactions" — Grade: 10/10

Covering all the transaction lifecycle, layers and protocols from TLS/SSL, TCP TLS Handshake, TCP/IP to End-to-End Security and Certificates and Encryption.