Sergei Udalov

Core backend for the Dixy mobile app: integrations, APIs, performance and delivery.

• Improved inventory synchronization 10x (20 min → 2 min) via ClickHouse→PostgreSQL migration, batch API-Hub integrations, and parallel incremental processing.
• Owned full-cycle delivery of cross-cutting backend changes (requirements → production) for a high-traffic mobile inventory and integration system serving 2,000 stores (~1,000 RPS, 800 GB+ data).
• Parallelized GitLab CI pipelines, cutting pipeline wait time from ~30 min to ~5 min for two engineering teams.

Banking infrastructure; technical leadership across three cross-functional teams.

• Led architecture and delivery of a banking infrastructure migration: rebuilt C4 documentation for ~50 services, introduced distributed tracing across 20 services, and drove the migration to ~80% completion.
• Designed and delivered an AI voice bot using LangChain and LLM orchestration, automating ~7% of routine customer payment inquiries.

Scalable e-commerce platform (consumer apps); launched products from scratch.

• Architected and delivered backend for 3 new consumer products from zero to production (150 RPS, 800K+ users, 20 GB data) — Kafka event streaming, WebSocket real-time layer, DDD boundaries.
• Built a Go platform service streaming Kafka events to WebSocket clients across multiple products, handling ~500 concurrent connections and ~50 events/sec.
• Built an AI code-review agent (Ruby service on GitLab webhooks) that analyzed changes against project conventions and flagged common security and performance issues.
• Established Domain-Driven Design as the architectural standard and a lightweight technical-debt process adopted by multiple product teams.

Lending-as-a-Service (LaaS) platform: credit automation, internal platform, Ruby standards.

• Built in the LaaS credit-automation domain; optimized core performance and SQL efficiency; led monolith→microservices extraction.
• Designed an internal RPC protocol and built the in-house "Core" framework adopted by multiple service teams.
• Increased system throughput and reliability; built a ClickHouse analytics module and business-event collection for analytics.
• Defined code-review standards and a Ruby competency matrix adopted across the engineering organization.

Nation-scale toll-road systems: Platon (truck toll collection), Oboz (freight documents), and Avtodor toll roads.

• Built reporting services and mobile APIs for Platon, a nation-scale toll-collection system (1M+ vehicles); implemented automated test pipelines and reliable test-database builds across modules.
• Extended the Oboz freight-document platform with document-processing and reporting capabilities for freight carriers.
• Built admin interfaces and payment reporting for Avtodor toll-road systems.

• Integrated the Idibu CV-advertising API with the Hiring Hub HR service; built a document-management system for ORAC (UK clients).
• Migrated projects from vendor-locked CI/CD (GitHub, Codeship, Heroku) to open-source GitLab CI and Dokku.

Backend services and public APIs for an SEO platform.

• Built the internal backend core — Sidekiq workers, remote RPC, RESTful API — and sped up JSON/XML/text generation for fast API responses.
• Worked on a high-load HTTP crawler in Go with RPC access; integrated the QIWI payment system.

• Reworked the core system's RPC API; migrated PGQ workers to the new internal API.
• Built a QIWI payment gateway via REST and financial report generators.

• Built a payment-acceptance API integrating PayPal, PerfectMoney and other gateways; automated financial reporting with Google Analytics.

• PHP/Symfony: online hotel-booking systems (HROS, High-Web). Ruby/Rails: 10+ e-commerce sites and in-house CMS (June Marketing); sports news portal with live broadcasts (Sportweek).