Artem Mishurchenko

About Me

Software Engineer with 7+ years of production experience across backend systems, Linux infrastructure, security and carrier-grade telecom. Focused on applied cryptography, secure system design and understanding systems at the protocol and OS level.

Work Experience

Support Engineer

PortaOne | May 2026 - Present

Investigated the security of SIP Digest authentication: recovered a 6-character test password in ~15 minutes on a laptop from a single captured request, then evaluated recovery time across password lengths to establish a recommended minimum password length.
Investigate production incidents in customers' carrier-grade VoIP systems, tracing issues to root cause and restoring normal service operation, resolving critical incidents within a 2-hour SLA.
Diagnose network, authentication and signaling failures by analyzing Linux system logs and SIP/RADIUS traces.
Cover 12-hour monitoring shifts watching a central Nagios alert dashboard; on each alert, notify the affected customer and open an investigation.
Coordinate maintenance and system upgrades with international telecom operators in real time to avoid customer-facing downtime.

DevOps Engineer

WinWin.travel · Volunteer | Apr 2026 - Jul 2026

Reworked the CI pipeline, cutting its run time from 60 to 5 minutes (12x faster) through caching, parallel jobs and removing redundant Docker container startups.
Migrated CI/CD pipelines from Bitbucket to a self-hosted GitLab instance.
Added AI code review to GitLab merge requests (PR-Agent with an LLM via OpenAI-compatible API, project-specific review instructions, inline comments) and automated Slack notifications with test results.

Full Stack Software Engineer

NDA | Jul 2025 - May 2026

Built a web platform for posting tenders and matching them with contractors (Django, JavaScript).
Developed a reusable Telegram shop platform for multiple clients, with a configurable admin panel, customization options and multi-language support.
Developed a React Native mobile app for improving creative thinking, built around daily challenges.

Full Stack Software Engineer

Lexima Tech | May 2021 - Jul 2025

Built a custom access-control API for 1Password on Nginx + OpenResty (Lua), enforcing fine-grained permissions and lowering licensing costs by reducing the number of required 1Password seats.
Executed an emergency database security lockdown overnight as part of a security incident response, working with a DevOps engineer under strict time constraints:
- restricted direct database access via IP whitelisting across 300+ services;
- rotated credentials for every affected service and introduced CI/CD pipelines for legacy services that had no automated deployment;
- assigned dedicated outbound IPs to Google Cloud Functions to keep them working under the new network restrictions;
- introduced role-based access with read-only database users, available only through VPN.
Built a data collection platform for the analytics team: scrapers for 20+ websites feeding a central database, with dashboards I set up in Google Data Studio (Looker Studio). Replaced manual data gathering that took 10 analysts ~2 hours each per day (~20 person-hours daily).
Designed and maintained ~200 Google Cloud Functions in a serverless architecture; migrated databases and services from Heroku to DigitalOcean and source control from GitHub to GitLab.
Maintained and optimized databases with 10M+ records, ensuring data integrity and query performance.
Built an internal browser extension automating routine tasks, used across the company and saving each user ~40 minutes a day.
Started as the sole engineer in the R&D department. As the team grew to 4, I took the senior role: reviewed the team's code, onboarded and mentored new engineers, gathered requirements with the product, marketing and operations teams, and wrote the technical specifications.

Full Stack Software Engineer

KlientWave - Digital Marketing Agency | Aug 2019 - May 2021

Built and maintained Telegram bots serving 50,000+ monthly active users.
Covered infrastructure work in a team without a dedicated DevOps role: deployed applications to Linux servers, configured CI/CD pipelines, took part in cloud migrations and infrastructure hardening.
Built an internal accounting system with expense analytics reports that helped the business spot unnecessary spending.

Projects

End-to-end encrypted messenger

Course project · Applied cryptography · Python

Designed a binary message protocol over TCP and implemented E2EE on top of it: ECDSA signatures, ECDH key agreement, HKDF key derivation and ChaCha20-Poly1305 authenticated encryption.
Implemented the Double Ratchet algorithm (used in Signal) for forward secrecy and post-compromise security.
Verified the protection with Wireshark by intercepting and tampering with traffic before and after encryption.

Task Tracker

Course project · YouTrack-inspired task tracker · Go

Built a Go backend (Gin) using clean architecture (handlers, services, repositories) with MongoDB and Redis.
Implemented passwordless authentication with WebAuthn (passkeys) and real-time updates via WebSocket.
Built a Next.js / TypeScript frontend; containerized the stack with Docker Compose behind Nginx, with Swagger API docs.

Technical Writing

I write about cryptography and systems internals on my blog (in Ukrainian). Selected posts:

Skills

Security & Cryptography

E2EE / Double Ratchet
ECDH / ECDSA / HKDF
AEAD (ChaCha20-Poly1305)
TLS / PKI
Access control
Secrets & credentials rotation
Infrastructure hardening

Systems & Infrastructure

Linux / Bash
SIP / RADIUS / VoIP
Nginx / OpenResty (Lua)
Docker
CI/CD (GitLab CI, Bitbucket, GitHub Actions)
GCP / DigitalOcean
Wireshark / tcpdump

Backend

Go / Gin
Python / Django / FastAPI / Flask
REST API / WebSockets
Third-party API integrations
PostgreSQL / MySQL / MongoDB
Redis / Kafka
Serverless (Cloud Functions)
Web scraping / Looker Studio

Frontend

JavaScript / TypeScript
React / SolidJS / Astro
React Native / Electron
HTML5 / CSS3 / Tailwind