Mykyta

MYKYTA KROKHALIEV
Backend Engineer | Node.js / TypeScript
Poland | Work authorized | On-site / Hybrid / Remote | Employment / B2B | [відкрити контакти](див. вище в блоці «контактна інформація») | LinkedIn

WORK EXPERIENCE
Outstaffing Agency (under NDA) | Backend Engineer (Part-time Contract) August 2025 – Present | Remote
• Built a NestJS game-aggregation service (100+ games) and payment integrations (2 payment aggregators) for a crypto
iGaming platform, owning both from design through production, all covered by Jest tests.
• Made interview preparation 3–4x faster by moving question search from manual work to a semi-automated pipeline of
embeddings, a reranker and an LLM judge.
Strix Dev | Backend Engineer October 2025 – August 2026 | Remote
Crypto arbitrage platform until February 2026, then entrusted with taking over Obscura from another team
• Designed and built real-time ETL over HTTP and WebSocket feeds from 4 prediction-market platforms (Polymarket, Kalshi,
Opinion, Predict.fun), tracking up to 100K markets at ~15K order-book updates and ~1K trades per second.
• Built the downstream NestJS microservices on NATS: a ClickHouse writer for full history, a price-event detector and a spread
service computing live spreads for ~10K matched market pairs in PostgreSQL.
• Reduced RAM usage from ~95% to a 40% peak and CPU from constant saturation to 70% on constrained servers by moving
ingestion to a dedicated host, compressing data, using B-trees for order books and cutting network calls.
• Cut ClickHouse order-book history queries from 100–150ms to under 10ms with a materialized view, at no extra load.
• Built order execution on Polymarket and API-based trading on Kalshi.
• Shipped a Jest-tested internal SDK wrapping 10+ exchanges in standardized HTTP and WebSocket clients, now used by
another large project and dozens of crypto trading bots.
• Designed a unified order-book abstraction that normalizes exchange-specific formats into ready-to-use state and recovers
from out-of-sequence and dropped updates.
• Added Redis- and WebSocket-based alerts with a React analytics UI; deployed services with Docker and Dokploy.
Helios Labs (outsourcing agency) | Backend Engineer December 2024 – October 2025 | Remote
• Owned the architecture of WL.BOT, a NestJS copy-trading platform serving 1,000+ RPS.
• Designed and built a batch parser service mapping a 2.5B-row Solana trade history in ClickHouse to traders; cut queries to
10–20ms and made PnL/ROI aggregations up to 100x faster with materialized views.
• Extracted two services from the monolith: a gRPC user service for strictly typed, faster lookups by other microservices, and a
service for in-session trading stats and PnL, referral and airdrop processing.
• Built filter-based whitelisting that adds up to 10K matching traders to a user's list at once, skipping existing entries.
• Built WebSocket notifications, a Telegram interface and BullMQ queues; operated services on Kubernetes (restarts, replica
scaling) with Prometheus and Grafana monitoring.
• Built backend services for GiftHunt, a Telegram Mini App with game mechanics and TON and Telegram Stars payments.
• Implemented deposit and withdrawal workflows across 3 microservices, coordinating transactions through asynchronous
RabbitMQ messaging and covering the flows with Jest tests.
Understat | Backend Developer January 2024 – December 2024 | Remote
• Reduced critical query latency by 76% (from 500ms to 120ms).
• Built ETL pipelines and BullMQ workflows loading semi-structured data from dozens of bookmakers into MongoDB.
• Added OpenTelemetry and Jaeger request tracing; supported incident response for a 24/7 production system.
Freelance & Startup Projects | Backend Developer 2022 – 2023 | Self-employed
• Built event-driven Kafka microservices, a WebSocket chat, an isolated Stripe payment service and OpenAI integrations for
Nika AI, an AI startup.
• Built Snack, a digital-goods marketplace with search, seller and admin dashboards, payment flows and product metrics.
• Built a GraphQL API with role-based access control on Prisma and PostgreSQL for a large media catalogue.
• Developed a Kafka-based order-processing engine for a crypto exchange prototype.

LANGUAGES & TECHNOLOGIES
Languages & Frameworks: TypeScript, JavaScript, Node.js, NestJS, Express.js
APIs & Architecture: REST, gRPC, GraphQL, WebSockets, microservices, event-driven architecture, distributed systems
Databases & ORMs: PostgreSQL, ClickHouse, Redis, MongoDB, vector search, Prisma, Drizzle ORM, TypeORM
Messaging & Queues: Kafka, NATS, RabbitMQ, BullMQ
Testing & Observability: Jest, Vitest, OpenTelemetry, Jaeger, Prometheus, Grafana, Loki
Infrastructure: Docker, Dokploy, Kubernetes, CI/CD (GitHub Actions, GitLab CI)
AI & LLM: AI-assisted development with Claude (PRD-driven specs, multi-agent orchestration), OpenAI API
Other: React, Stripe, TON