Backend developer & freelancer
Client and own projects: Telegram bots and AI integrations, site migrations and security, scrapers and catalog sync, IoT payments.
reference-web-development
You show a site whose look and structure you like; I build a new one in the same spirit with your content and brand. First a written brief of the reference (layout, colour, type, spacing, breakpoints, motion), then the build, then a measured check against the reference at desktop and phone widths. Nothing of the reference's text, photos, logos or fonts is copied.
v2v-demo
A bilingual (UK/EN) voice-and-text AI concierge engine with three interfaces on one API — Telegram bot, Telegram Mini App (Voice-to-UI, server-owned cart, Telegram Stars) and web — running ten independent business assistants (dental, auto, real estate, cleaning, translation, beauty salon, barbershop, restaurant, pizzeria, acupressure shop) behind one inline picker, sharing a single grounding-gate core. An automated scenario-probe tool caught a real safety-relevant bug (a sedation request getting scheduled as a routine booking) before it reached a user. One main dependency. Live demo: @v2v_demo_bot on Telegram (Open Concierge opens the Mini App) and web.pere.org.ua.
vending-esp32-monobank
Lets a commercial Rheavendors coffee machine take Monobank QR payments directly, with no payment intermediary and no monthly fee: a Cloudflare Worker verifies each payment against the Monobank API and queues it in a per-machine Durable Object, and an ESP32 polls it and credits the machine through an optocoupler-isolated board on the coin connector. Acknowledged queue, no double payouts, the machine's own Ready state respected. Verified end to end on the customer's machine with real payments.
php-vulnerability-audit
Audit and patching for the critical PHP interpreter flaws CVE-2026-109618 and CVE-2026-109619 (PHP2Shell, fixed 21 Oct 2026): an inventory of every host and the PHP version its web server really serves, an upgrade to 8.2.35 / 8.3.36 / 8.4.27 / 8.5.12, a vendor backport or a migration for end-of-life branches, temporary mitigations from the PHP advisory where the patch must wait, worker restarts, a check from the web side, a log review for exploitation signs and rotation of secrets that may have been exposed.
site-security-cleanup
Full recovery of hacked WordPress, Joomla and OpenCart sites: hidden mobile redirects, web shells and backdoors, spam injected into the database, Google Safe Browsing and hosting blocks. Isolated staging, diff against clean CMS cores, database sanitization, PHP 8.2+, no PHP execution in upload folders, 2FA, WAF and a Search Console review, with 100% data preservation.
tilda-migration
A turnkey move of a business site or online store off Tilda onto Horoshop, Weblium, WooCommerce or Shopify: the design and structure kept, a 301 redirect map for every URL, meta data carried over, Ukrainian payments and Nova Poshta connected, orders pushed to Telegram and the CRM, and the main domain switched with no downtime.
opencart-catalog-migration
Migration of a live online store with 10,000+ SKU from OpenCart 1.5/2.x, PrestaShop 1.6, VirtueMart or a custom CMS to OpenCart 3/4 on PHP 8.2+ or Horoshop: attributes, options, customers with password hashes and order history carried over, content cleaned, MySQL and caching tuned, images in WebP, old SEO URLs mapped to 301 rules.
marketplace-catalog-sync
Automated export, normalization, mapping and import of large catalogs between Prom.ua, Rozetka, Horoshop, OpenCart, Zakupka and Epicentr, built on the Go core of feedsync: category correspondence matrix, a pre-validator against Rozetka's moderation rules, cleaned descriptions and photo checks, and feeds refreshed every 30-60 minutes.
marketplace-harvester
Collects product catalogs from marketplaces and competitor shops (Prom.ua, Rozetka, OLX), normalizes them and delivers import-ready YML/XML/CSV feeds for OpenCart, Shopify, WooCommerce or Prom.ua, or pushes them into KeyCRM. API-first collection with a headless browser as the fallback; a daily repricing module warns in Telegram or adjusts margin automatically.
google-maps-lead-extractor
Builds fresh B2B contact lists of local businesses in a chosen region or country from Google Maps and directories: a multi-language search grid (local language, English, Ukrainian), non-target categories filtered out, phones normalized to E.164, deduplication by Place ID and coordinates, emails and social links crawled from company sites, delivered into a live Google Sheets table.
listings-sniper-bot
A Go service that watches classified boards for new listings every 2–4 seconds and pushes the good ones to a closed Telegram group within seconds: photo, the seller's number, the price gap to the market and a link. Resellers and duplicates are filtered out on the fly; no browser involved.
prozorro-tender-intelligence
Reads the open Prozorro REST API directly, finds the tenders that fit a supplier by CPV code and by the text of attached PDF/DOCX documents, analyzes winners, discounts and competitor pricing per procuring entity, and sends a prioritized digest every morning at 08:00 to Telegram or email, with Metabase dashboards.
zero-downtime-migration
A seamless move of WordPress, OpenCart, Laravel and custom sites to a new server or a new domain with zero downtime: staging tested through a hosts entry, TTL lowered ahead of release, a final delta sync, serialization-safe URL replacement, one verified redirect setup with a 301 map, and corporate mail kept intact (MX, SPF, DKIM, DMARC).
fastshop
A 30,000-product OpenCart store built as an overlay on stock OpenCart: faceted filters with counts and one canonical SEO URL per filter state, a one-page checkout with a Nova Poshta city/branch picker, Redis cache, WebP and a lean theme. Against stock OpenCart on the same data: catalog page 34 ms to 10 ms, search 267 ms to 5 ms, Lighthouse mobile 100 with a 19–28 KB page. 37 end-to-end checks.
crmbridge
Connects a shop or Telegram bot, Binotel telephony and Nova Poshta to a SalesDrive CRM: one deal per order even when the site retries or the CRM loses a reply, caller cards for managers, missed calls as leads, and parcel statuses that move the funnel forward only. 250 tracked parcels take 3 Nova Poshta requests. 25 tests under the race detector.
fiscalgate
Turns confirmed Monobank and LiqPay payments (and cash on delivery) into Checkbox PRRO fiscal receipts exactly once: 300 orders × 4 concurrent webhook copies give exactly 300 receipts, a lost register reply never doubles a receipt, prepayment plus cash on delivery becomes one receipt with two tenders, and refunds become return receipts. Shift and Z-report on schedule. 26 tests under the race detector.
feedsync
Turns supplier price feeds (YML/XML, CSV, JSON) into Rozetka and Prom.ua price lists and syncs an OpenCart product table: streaming read, every published file re-validated independently, atomic publish. 25,000 offers in about 1.5 s and 36 MB; 100,000 in 6–7 s; a repeat OpenCart sync changes nothing (≈25 ms).
An AI system that creates, tests and runs ad campaigns for a Shopify luxury-fashion store, end to end: Claude turns live store data into hypotheses, a chat agrees the creative brief and produces preview and final videos (ffmpeg montage, captions checked against the approved script), Meta campaigns are assembled — always paused — and every ad gets a verdict by reconciling against real Shopify orders, not the ad pixel. Anything that moves money is a proposal the client confirms. Three stages: the first two accepted, the third in acceptance.
bid-triage
A bid-screening system for freelance-platform clients drowning in AI-generated proposals: instead of detecting authorship (an arms race that favors the generator), it prices the interaction — a deterministic fluff-strip filter, then one deadline-gated canary question a real practitioner answers in a line and a generic pipeline can't. The same mechanic generalizes to any high-value, low-volume screening decision (B2B tenders, security-disclosure triage) — scoped conservatively per client, not sold as a shared SaaS product.
landing-turnkey
Two original landing-page design directions for the common one-page-site request: a bright, discount-driven product page and a dark, portfolio-style business/services page, each built around a single call to action and a lead-capture form.
ragline
AI/RAG Telegram support-bot backend: Postgres full-text search retrieval, a pure escalate/generate/cache decision that never repeats a low-confidence guess (even from its own cache), and a version-gated answer cache that invalidates on document edits. Proven live: a real retrieval bug (stopword-driven false matches) found and fixed against seeded fixtures, then a document edit correctly forced regeneration instead of serving a stale cached answer.
subgate
Telegram paid-channel-access REST API: idempotent payment-webhook ingestion (gateway redeliveries absorbed via a UNIQUE constraint) and a membership state machine (active/grace/expired) that survives a concurrent expiry sweep. pg_advisory_xact_lock(subscriber_id, channel_id) serializes renewals against sweeps. Proven live: 10 concurrent identical webhook deliveries produced exactly 1 payment row; 5 concurrent renewals racing 5 concurrent sweeps landed deterministically active.
geopulse
GPS fleet-tracking REST API with exactly-once geofence enter/exit detection from a position stream that duplicates and reorders — the real failure mode of GPS trackers. pg_advisory_xact_lock serializes concurrent pings per vehicle; PostGIS ST_DWithin handles containment. Proven against direct database state: a burst of concurrent/rapid pings produced zero spurious events across the full test session.
slotwise
Appointment-booking REST API where double-booking prevention is a Postgres EXCLUDE constraint (tstzrange + btree_gist), not an application-level check — no race window under concurrent requests. Proven live: two simultaneous overlapping booking requests against the running server return exactly one 201 and one 409. Booking state machine, Telegram reminders with a zero-credential fallback.
fleet-crm
Fleet/logistics CRM REST API — JWT auth, a checked work-order state machine (not a free-form status column), invoicing gated on completion, and a telematics webhook. Found and fixed a real cross-entity bug (a partial-update fix that prevents vehicle data loss on every status change) before the first commit — verified end-to-end via a live docker compose run, not just unit tests.
tumanomir
Go CLI implementing a published methodology for measuring AI-spec ambiguity as three metrics (K_drift, D_const, D_pair). 66 commits, zero reverts, gates its own specification in CI. Rewrote the K_drift scanner for a 233x allocation reduction; found and documented a naming-noise floor in the generation-spread metric.
fix-review
Multi-agent PR review pipeline: fans a diff out to 3 parallel models with a read-only 5-tool CLI fallback cascade, then a Claude arbiter verifies each finding against real repo state before acting. In production since June 2026: 22 PRs reviewed, 69 review rounds, 81 raw findings but only 2 confirmed fixes — replaced a permission-bypass CLI tier with a verified read-only cascade.
Built out a modular, conversation-first sales CRM across 1,366 commits in 3 months — AI-powered reporting through a provider-fallback gateway (Gemini → OpenRouter), a deterministic decision-billing ledger, lead ingestion/enrichment pipelines, and org-level access control. ~123K LOC across frontend and edge functions, 201 test files, 23 production cron jobs.
Took over and substantially rebuilt a gym-cleaning operations platform after its no-code MVP stage. Delivered mobile-first cleaner workflows with AI photo validation, automated escalation triggers, and multi-provider LLM failover across 991 commits in 3 months — 42K LOC, 474 passing tests, zero npm vulnerabilities.
Conversational AI assistant (Telegram bot) for a Ukrainian application-writing consultancy. RAG + LLM fills Excel templates while preserving formula chains. 8-week solo delivery: 65 sessions completed, 100% Excel artefact validity, 22% escalation rate.
Built a voice AI agent automating 80% of 20,000 monthly support calls for a micromobility company. Delivered in 24 days: Go backend, Binotel webhooks, Whisper STT, GPT-4o-mini function calling, ElevenLabs/Azure TTS, Redis session state.
Developed enterprise DevOps platform components for CloudBees CD/RO serving Fortune 500 clients. Created 50+ reusable plugins in Java, Groovy, and Perl, reducing code duplication by 60% and achieving 95% automated test coverage.
Led Kyiv development team for 5+ years building core components for PortaSwitch BSS, Billing, and Softswitch platform serving MNO/MVNO/MVNE, cable, VoIP, and IoT providers. Architected billing solutions with 99.9% system reliability.
Architected complete redesign of enterprise email platform mail.ua serving 1M+ active users. Managed 20+ backend engineers through 3-year platform transformation, transitioning from Waterfall to Agile with automated testing pipelines.