Anton Koshcheev

Koloq.co·Founder / Applied AI Engineer (solo, side project)·koloq.co·2025-05 — Present

• – Built a production LLM pipeline turning multilingual Telegram chat messages into structured rental listings (30+ typed fields: price, dates, geo, amenities). Prompts, validators and mappers are generated from a single tag definition — new fields propagate with zero manual edits. 7k+ listings extracted to date; 200–700 live listings in each major city.
• – Designed an internal LLM gateway: multi-provider routing (Vertex AI Gemini, OpenAI-compatible), per-route RPM/RPD/TPM quotas, priority queue isolating interactive from batch traffic, circuit breaking and retry classification, full OpenTelemetry metrics with Grafana dashboards and alerting.
• – Cut classification cost ~40% with a 4-stage cascade (zero-cost heuristics → embedding classifier → batched cheap LLM → full extraction); every stage fail-open, rolled out per-source in shadow mode.
• – Trained the embedding relevance classifier (768-dim embeddings + logistic regression, 5-fold CV): F1 0.971, 0% cross-validated false negatives. Shadow evaluation caught a production domain shift (FN spiked to 13.6%); retrained on 8.1k examples with class-imbalance handling and threshold recalibration — FN restored to 0.7%, hot-swap deploy.
• – Built an eval harness over a hand-labeled golden set (150 examples, 9 strata, 20% held out): per-field accuracy with asymmetric FN/FP costs, fabricated-field rate, JSON validity, p50/p95 latency, $/1k messages. Benchmarked 10 models against the production baseline and migrated to one matching quality at ~2.5× lower cost, with a documented rollback path. Every inference carries a SHA-256 hash of its effective prompt, so eval runs and production rows attribute to an exact prompt revision.

TypeScript · Node.js · Python · scikit-learn · Vertex AI (Gemini) · OpenAI API · PostgreSQL/PostGIS · OpenTelemetry · Grafana

Kraahl·Founding Engineer·Hybrid, Paris·2025-05 — Present

• – Grew a collectibles auction marketplace to six-figure monthly GMV in 14 months — real-time auction engine, multi-provider checkout (Stripe, PayPal) across 6 currencies, cross-border shipping (Shippo), 220+ sellers onboarded.
• – Re-architected the founder’s LLM-prototyped (vibe-coded) features into a contract-first hexagonal core — one shared Zod contract package consumed by web and mobile — with a skill library and hard review gates so LLM coding agents produce architecture-conformant code by default.
• – Enforced fintech-grade testing on the money path: walking-skeleton pipeline tests for every money flow on both payment rails, 60 CI fitness tests that fail the build on architectural violations, and a real-database integration gate on every PR (173/173 green).
• – Shipped two production LLM features: an ops copilot — a tool-calling agent over the marketplace admin APIs (orders, refunds, partial payments, disputes), the operator asks “what happened with order 3154” instead of running probe scripts, every run trace-logged in Axiom — and multimodal (text + image) listing moderation with a persisted audit trail and human override.
• – Designed the transactional core (PostgreSQL, strong consistency under concurrent writes) and a self-healing money path — idempotent webhook handling, payment-recovery replay, 15-minute provider↔DB reconciliation — coordinating money across Stripe, PayPal and Shippo; zero data-integrity incidents in production.
• – Ran the product loop, not just the code: every feature shipped as a hypothesis against a driver tree, demand-funnel instrumentation to measure it, and in-database analytics (cohort retention, sell-through, seller-concentration risk) deciding what to build next.
• – Kept the site fast and up through drop-day traffic spikes: optimized hot paths for surge concurrency and rebuilt the image pipeline around an explicit CDN cache-key cost model, sharply cutting page weight and load times.

TypeScript · Node.js · React/Next.js · Expo/React Native · PostgreSQL · Supabase · Stripe · PayPal · Shippo · Axiom

Starknet Ecosystem·Open-source Engineer, OnlyDust grants·Remote·2023-05 — 2024-12

• – Grant-funded via OnlyDust: ~20 PRs merged across Beerus (Rust, Starknet light client), starknet-devnet (Python, testing infra) and Pathfinder full node — shipped in pre-spec territory, reverse-engineering undocumented hashing and encoding conventions across ~6 repos.

Rust · Cairo · Python · TypeScript

Ozon Tech·Backend Engineer, Retail·Moscow·2022-05 — 2023-01

• – Owned 3 gRPC services in the retail domain (~10 interconnected services, peak ~50k RPS, sub-100ms p99); built Kafka pipelines for the order-status flow.
• – Introduced Jaeger tracing and structured logging, cutting median cross-service debug time from ~3h to ~40min; led ~6 production incident investigations.

Go · gRPC · PostgreSQL · Kafka · Kubernetes · Prometheus · Grafana · Jaeger · TypeScript · React

Skyrex·Backend Engineer (Crypto Trading)·Moscow·2020-06 — 2022-01

• – Built the trading MVP from scratch: order-execution engine, portfolio tracking, Binance API integration, event-driven RabbitMQ pipeline (p99 routing < 150ms).