Nikolai Vasilev
Golang Developer @Rainforest
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WORK HISTORY
Golang Developer @Rainforest
US
Own core payment processing services for an embedded payments platform purpose-built for vertical SaaS — processing billions in annual volume across card, ACH, Apple Pay, and alternative payment methods. Design and implement Go microservices for merchant onboarding, transaction orchestration, and real-time settlement, ensuring PCI DSS compliance at every layer. Drive webhook-based event architecture for payment lifecycle notifications and integrate third-party acquiring and risk providers.Stack: Go, PostgreSQL, Redis, Kafka, gRPC, REST, Docker, Kubernetes, AWS, Prometheus, Grafana, DatadogKey results:→ Designed merchant onboarding service handling KYC/KYB verification flows with automated risk scoring — reduced merchant approval time from 48 hours to under 15 minutes for 80% of applications→ Built multi-acquirer transaction routing engine in Go with configurable fallback logic and real-time BIN lookup — improved authorization rates by 12% and reduced processing failures by 30%→ Implemented webhook delivery system with at-least-once guarantees, retry with exponential backoff, and dead letter queue — serving 2M+ webhook events/day at p99 under 200ms→ Reduced settlement reconciliation errors by 70% by building an event-sourced ledger service with penny-perfect reporting and automated daily deposit calculations→ Integrated PayPal/Venmo as alternative payment methods via single unified API, enabling platforms to accept 5 payment types through one checkout flow with zero additional onboarding
EDUCATION
Peter the Great St.Petersburg Polytechnic University
Computer Science
ABOUT NIKOLAI VASILEV
WhatsApp: https://wa.me/44••••••••62Senior Go Developer with 7+ years of experience building high-load backend systems: ad platforms, chatbots, billing, real-time communications, and fintech payments. Decompose monoliths into microservices, design event-driven architectures on Kafka (DLQ, retry, idempotency), and establish full observability stacks from scratch.Key highlights:→ Decomposed two production monoliths (Java → Go, Kotlin → Go) using Strangler Fig pattern with zero-downtime migration→ Scaled systems handling millions of ad impressions/day and messages/day (p99 < 100ms)→ Reduced infrastructure costs by 35%, cut p95 latency by 40%, and boosted paid conversion by 25%Tech stack: Go, PostgreSQL, YDB, Kafka, Redis, gRPC, GraphQL, MongoDB, ScyllaDB, ClickHouse, Docker, Kubernetes, Prometheus, Grafana, Jaeger, ELK. English C1 — fluent in international team communication.
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