Nikita Kalinskii

Lead the development of cards payments processing system with PCI DSS compliance. System is 50/50 Golang/Scala. Overseeing its architectural evolution, integration of new acquirers, maintenance and development of new features in the anti-fraud system. Lead the team of 2 backend engineers. Planned and distributed tasks within the team using the Kanban methodology. Led and successfully executed the migration of the system from on-premises servers to Kubernetes and AWS, reducing infrastructure costs by 60%, and increasing system reliability through multi-AZ support. Took part into integration of modern CI/CD pipelines (Gitlab CI, ArgoCD) from scratch, reducing testing and deployment time from 3 days to 1 day on average. Introduced a comprehensive monitoring system (metrics, alerts, logging), reducing incident response time from 5 to 6 hours (when reported by customers) to 10 to 15 minutes through automated notifications.

Designed and developed bank operations feed event-driven system handling over 100M operations per day (~1200 per second) with 99% availability using Kafka, Couchbase, and Elasticsearch Migrated a 2TB operations dataset from Oracle to Couchbase using a fully asynchronous DCP streaming client, ensuring minimal impact on database performance Optimized the accounts service, refactoring legacy parts to ZIO, increasing throughput by 30% (from 450 to 600 RPS), and improving reliability with circuit breakers, fallback caches, and rate limits. Designed and developed a new accounts access restriction service (REST API, PostgreSQL) in Go Acted as one of the tech leads for the Scala community, contributing to: a new HTTP server library (with Tapir & Tofu); an in-house metrics librar; and CI/CD for Scala projects; an in-house Kafka library simplifying metric/log integration and consumer-handling strategies. Researched and mitigated potential risks during the migration from legacy cloud infrastructure to Kubernetes.

Developed from scratch mobile app for digital document exchange and signing: documents feed with different filters, pagination, per-document actions domain Used RxJava (reactive programming framework) for main logic Implemented security module: user data encryption with password and biometry Implemented ability to sign documents with cloud signature right in the app with ability to choose certificate and confirm by SMS/Push