Alexander Kosachev

Developed and modernized a backend system for managing 10,000+ Bitcoin miners within a monorepo (core service + supporting services). Refactored legacy parts by migrating data access from TypeORM to Kysely, simplifying a Query Bus, and reducing DI complexity by consolidating approaches in the monolith. Built an asynchronous operation model for long-running tasks (operation initiation, later result retrieval). Implemented miner performance processing, operational status tracking, and reporting for data-center administrators and business stakeholders. Developed services deployed on Kubernetes with workload-based scaling. Also built a custom GUI-based AI coding agent in Rust to perform safe large-scale codebase changes.

Built payment platform backend services including payment processing and invoicing, designing solutions from business requirements. Implemented an asynchronous model for long-running operations using persisted operation entities, returning operation IDs immediately, and handling processing in separate services. Delivered APIs to check status and results, cancel operations, and submit missing information with validation. Used Kafka to forward payments for further processing and to publish events for push notifications; developed producers/consumers and defined message-broker interactions. Fixed critical invoicing issues and refactored complex legacy logic. Created internal libraries for JWT, logging, configuration, and telemetry, using PostgreSQL transactions and indexes.

Helped build a new banking platform backend from scratch by independently designing and implementing microservices. Developed authentication/authorization with Keycloak integration. Built integrations with government information systems and credit bureaus for sending and retrieving data. Implemented a user-registration flow as a Camunda workflow, with backend workers processing queued tasks for each stage. Developed RabbitMQ producers/consumers with correct Ack/Nack handling. Created reusable Go libraries for JWT, logging, configuration, context enrichment, and graceful shutdown across services. Implemented an inter-service/external integration HTTP client based on fasthttp with connection reuse.