Sergey Yakushevich's Resume

Sergey Yakushevich

Senior Backend Engineer (Go, Ruby)

Batumi, Georgia

cyberjosef.devsergeyayya@gmail.com+48530213401github.com/sergey-yakushevichlinkedin.com/in/sergey-yakushevich-688a4b179
Sergey Yakushevich's profile picture

About

I have spent 10 years on backends, and the last 5 of them on payment systems. At Moyasar I built fraud blocking and regulatory KYC on a platform that has processed 350M+ payments across 10+ microservices. Before that I shipped Visa installments and PCI-DSS card tokenization at Mondido, and rebuilt banking integrations at Regate. I take a feature from schema design through to the alert that pages someone when it breaks in production. Most of my career I used Ruby, but I write Go now as well, and I am looking for backend roles in Ruby or Go.

Work Experience

Moyasar,Senior Ruby on Rails Engineer

Dec 2025 - Aug 2026
  • Ruby on Rails
  • PostgreSQL
  • Microservices
  • Kafka
  • Fraud Detection
  • Built the fraud system that scores and blocks transactions on risk signals, on a platform that has taken 350M+ payments across 10+ microservices.
  • Shipped identity verification to the regulator's spec. We needed it to expand into new markets.
  • Wrote the alerting for payment flow disruptions and took time to detection from hours to seconds. We hear it from a monitor now rather than from a merchant.
  • Analysed on my own initiative which platform features merchants actually use, and handed management the numbers. Sales now leads with the most adopted features when pitching new clients.
  • Sat in on sales calls as the technical voice when a prospective merchant had integration questions.

Mondido,Senior Ruby on Rails Engineer

Jan 2024 - Jan 2026
  • Ruby on Rails
  • React
  • PostgreSQL
  • PCI-DSS
  • Card Tokenization
  • Visa
  • Delivered the Visa installment integration end to end, backend and checkout UI, which added a payment option merchants had been asking for.
  • Built PCI-DSS compliant card tokenization for gateway calls, so raw card numbers stayed out of our systems.
  • Compared several audit log designs, then built the one that traces every merchant and staff action without adding latency to the request path.

Regate,Senior Ruby on Rails Engineer

Nov 2021 - Jan 2024
  • Kafka
  • Event-Driven
  • AWS
  • Kubernetes
  • Terraform
  • Ruby on Rails
  • Automated per-pull-request AWS environments in CI. Reviewers got a running app instead of a screenshot, and release quality went up with it.
  • Owned the integrations with the payment and banking APIs that drive the automated accounting workflows.
  • Started the Service Layer refactor that pulled business logic out of callback-heavy Rails models, which is what made the codebase safe to change again.
  • Raised RSpec coverage and added CloudWatch dashboards, so regressions surfaced in CI rather than in production.

iTransition,Software Engineer

Jan 2016 - Jun 2020
  • Kafka
  • Elasticsearch
  • Microservices
  • GraphQL
  • AWS ECS
  • Ruby on Rails
  • Moved the main search workload off MySQL onto Elasticsearch and made it 90% faster for 50M+ users.
  • Made the test pipeline 5x faster, which took a full release cycle down from days to hours.
  • Weighed the service communication options and introduced Kafka, which is what let the microservices stop calling each other synchronously.

Education

Belarusian State University

2013 - 2018
Bachelor of Science in Computer Science

Skills

  • Go (Golang)
  • Ruby
  • Ruby on Rails
  • Concurrency & Message Queues
  • Kafka
  • API Design (REST & GraphQL)
  • PostgreSQL
  • Redis
  • Elasticsearch
  • Docker
  • Kubernetes
  • Terraform
  • AWS (EC2, RDS, S3, Lambda, ECS)
  • CI/CD (GitHub Actions)
  • Event-Driven Systems
  • Microservices
  • Distributed Systems
  • OAuth2 / JWT
  • Payment Gateway Integration
  • PCI-DSS Compliance
  • 3DS Authentication
  • Card Tokenization
  • Fraud Detection
  • Identity Verification (KYC)
  • English (C1)