Andrei Velent

Lead full-stack engineer — built from the init commit, ~80% of 1,099 commits (~334,000 lines: PHP, Go, TypeScript)

Full-cycle multi-supplier platform for tours, hotels and flights: search → pricing → booking → payment → document issuance.

• Designed the payments subsystem end to end: two-stage acquiring (hold → capture/void → refund) with split payments across sub-merchants — a pre-flight check of every recipient eliminated partially captured payments; capture is event-driven over RabbitMQ, so a payment failure can never roll back a confirmed booking.
• Integrated 6 travel suppliers behind a single adapter port — hand-built SOAP for a flight GDS with ticketing/void, session-managed XML for tour operators — and passed Expedia Rapid partner certification.
• Built a Go engine that deduplicates ~1M hotel records from 5 suppliers against a 700k canonical catalog: a spatial grid index turned an O(N²) scan into a neighborhood scan, an 8-metric similarity ensemble does the matching, and every merge is reviewable and reversible.
• Cut a chronic 48-hour supplier sync by ~7× and shrank the incremental sync window from 66 days to one day with watermark syncs, hash-rotated refresh and configurable worker pools.
• Stood up observability from zero: 15 Grafana dashboards, custom metrics over RoadRunner RPC, end-to-end tracing; CI with 6 security scanners and diff-based mutation testing.

PHP 8.4 · Symfony 7.4 · RoadRunner · Go 1.23 · PostgreSQL 17 · RabbitMQ · TypeScript

Built from scratch — author of the first commit, largest contributor (~69,000 lines)

A white-label e-commerce/food-delivery SaaS: one codebase, many branded tenants — web, iOS and Android.

• Designed and built schema-per-tenant multi-tenancy as a custom Symfony bundle: dynamic connection switching at the Doctrine DBAL level, migrations across all tenant schemas in one command, tenant context propagated automatically across the async message bus — the foundation the whole product runs on.
• Made Doctrine schema introspection work in a multi-tenant setup (custom PostgreSQL platform + schema manager) — without it, schema diffs simply don't work in schema-per-tenant.
• Built a white-label mobile pipeline: a branded native iOS/Android app per tenant — palette, deep links, signing keys, store assets — generated from config and built by CI at the push of a button in the admin panel.
• Delivery geo-zones on PostGIS polygons with a business-hours engine implemented twice — PHP and PL/pgSQL — with test-enforced parity, so "the nearest open location" is answered inside the database.
• Guaranteed order delivery to restaurant POS systems (iikoCloud, Frontpad, Caffesta): DB-backed queue, retries with backoff, deferred send for closed locations.

PHP 8.3 · Symfony 7.2 · API Platform 4 · PostgreSQL 16 + PostGIS · Docker Swarm

Lead developer — designed and wrote the platform from scratch: ~700 of 1,285 commits (~115,000 lines)

A production food-delivery platform running a national restaurant brand's online ordering in Belarus.

• Bootstrapped the entire platform — order domain, event-driven architecture, JWT auth, role model — and kept it in production for 3 years as the sole architect.
• Payments with two acquiring banks behind one interface, card tokenization (PCI-DSS-safe, cards never stored), recurring payments and partial refunds down to a single order-line modifier with a full refund journal.
• Real road-network delivery routing on self-hosted OSRM — the nearest restaurant is chosen by driving distance, not a straight line; audited and fixed the geo data of the entire customer base with self-hosted Nominatim.
• Schedule engine on native PostgreSQL range types with ~10 custom Doctrine DQL functions — "is the restaurant open right now" is computed entirely on the DB side.
• Cascade SMS delivery (cheap Telegram-OTP first, SMS fallback on TTL) via custom Symfony Notifier transports — cut per-order notification cost; Firebase + Huawei push for the local market.

PHP 8.3 · Symfony 7.2 · API Platform 3 · PostGIS · OSRM · RoadRunner · Redis

Started the codebase and led it for 7 years — top contributor: ~3,330 of 9,474 commits, ~602,000 lines added

A multi-tenant food-delivery marketplace: restaurants, courier logistics, online payments, partner back-offices, mobile APIs.

• Designed the distributed courier-dispatch engine (95% authorship): a DB-configurable state machine on RabbitMQ that survives worker restarts, PostGIS geo-scoring, order chaining (2–3 orders per courier by geometry and cooking-time ETA), and pool-mode M×N assignment-problem resolution under distributed locks.
• Built the marketplace payment core (91% authorship): three acquiring banks with three different crypto-signature schemes, two-phase auth/capture with automatic revenue splits across restaurant, courier and platform, mutual-debt netting, and kopeck-exact rounding reconciliation for bank settlement.
• An internal ledger of restaurant and courier balances — snapshots, compensations, payouts to self-employed couriers — plus tips, card-on-file and partial refunds accurate to the sub-merchant.
• Order-pricing engine with 20+ discount/promo mechanics with explicit priorities and exclusions, shared carts with per-participant settlement, dynamic delivery pricing by geo-zones and distance.
• Executed zero-downtime platform migrations over the years: PHP 7→8, Symfony 4→6.4, PostgreSQL→14, and PHP-FPM → RoadRunner (100 persistent workers) with a full statelessness audit.

PHP 8 · Symfony 6.4 · PostGIS · TimescaleDB · RabbitMQ · Redis TimeSeries · Elasticsearch · Mercure

Senior engineer — owned the payments/billing subsystem (~2,900 lines in 3 months)

A fintech platform for paying international contractors by bank transfer or crypto (Python).

• Multi-currency settlement pipeline: approved invoices aggregated into project invoices and bank payment orders, FX conversion at historical rates with Decimal-exact fee accounting, documents generated from Jinja-DOCX templates to PDF.
• FX reference-data service — Fixer.io catalog and daily cross-rates on a DB-configurable schedule, async-cached point-in-time rate lookups; payment methods for bank rails and BSC crypto payouts.

Python 3.11 · FastAPI · async SQLAlchemy / SQLModel · PostgreSQL · Django admin

Senior engineer — designed and shipped the listing-scraping subsystem (~1,270 lines, one production PR)

A long-term rental marketplace: listings, digital contracts, e-signing, market monitoring (Python).

• Template-method scraper framework: new listing sources plug in as ~100-line declarative subclasses; 5 production scrapers across 4 ingestion strategies, including a reverse-engineered Hasura GraphQL API with cursor pagination — two countries, rental and sale markets.
• Incremental scraping with URL-keyed dedup and early-stop, an append-only price-history time series, a hardened S3 image pipeline; runs as 10 staggered Celery beat jobs on a dedicated RabbitMQ queue.

Python · Django 4.2 · Celery · PostgreSQL · RabbitMQ · BeautifulSoup · AWS