Alexander Aprelkin

I help companies fix and improve critical backend systems — especially payment flows, real-time integrations and unstable production services.

More than 10 years experience.

Senior Backend Consultant for Payment and Real-Time Systems.

Java , Kotlin, Python, Spring Boot, Quarkus, Cloud, ML

Selected Project Experience

2021 – Present | Corporate Payments / FinTech

Senior Software Engineer – Payment Processing Platform (Issuer Side)

• Development and stabilization of a highly available real-time authorization system in live payment processing (24/7 production)
• Processing and routing of international credit card authorization requests
• Forwarding authorization requests to an external issuer-processing platform
• Integration of external payment networks and airline/corporate booking systems
• Investigation and resolution of critical production incidents in live payment traffic
• Root-cause analysis across multiple system boundaries (network, processor, internal services)
• Migration of authorization services to a containerized Kubernetes cloud environment
• Development of internal operational and analysis tools for support and operations teams

Technologies: Java, Spring Boot, Kafka, TCP/Netty, Docker, Kubernetes, Azure Cloud, 2020 – 2021 | Omnichannel Retail Plattform

Senior Software Engineer – Order-Management-System

• Development of business-critical backend services within a distributed omnichannel order-management platform
• Implementation of Available-to-Promise decision logic for real-time order validation
• Integration with enterprise retail systems
• Event-driven communication via Kafka

Technologies: Java, Kotlin, Spring Boot, Kafka, Kubernetes, Docker, GCP, PostgreSQL,

MongoDB

2019 – 2020 | High-Traffic Digital Plattform

Senior Software Engineer – Publishing Plattform

• Development of a high-traffic online platform with real-time personalized content delivery
• Contribution to recommendation and experimentation systems (A/B testing, ML-

supported decisions)

• Processing large volumes of user interaction events through streaming pipelines

Technologies: Java, Python, Kafka, Kubernetes, Docker, AWS, Elasticsearch

2018 – 2019 | FinTech Billing System

Senior Software Engineer – Credit Card Billing

• Development of billing and statement generation service for credit card transactions
• Aggregation and processing of financial data from SAP and CRM systems
• Integration of an output management system for document generation (PDF statements)

Technologies: Java, Spring Boot, Kafka, MongoDB, Azure Cloud, Docker 2017 – 2018 | E-Commerce Fulfillment

Senior Software Engineer – Logistics Platform

• Development of cloud-native microservices for automated warehouse and order processing
• Synchronization of inventory and order states via event streaming

Technologies: Java, Spring Boot, Kafka, Kubernetes, Docker, MySQL

2017 | Risk & Fraud Analytics (FinTech)

Machine Learning Engineer

• Development of machine-learning approaches for fraud and anomaly detection in financial data
• Training and production usage of ML models

Technologies: Python, Java, Machine Learning, PostgreSQL

Earlier Consulting Projects (IT Consulting)

Insurance — Claims Management System

Backend development for customer contact center platform of an international insurance provider.

Telecommunications — CRM Migration Systems

Modernization of a Java-based CRM system and preparation of large-scale customer data migration.

Telecommunications — Event Processing & Billing

Development of an event-processing system for aggregation and billing of telecom usage data.

Technologies: Java, Spring, Java EE, Oracle DB, Apache Flink, Messaging-/Batch-

Verarbeitung, Microservices · REST APIs

Technologies (Excerpt)

Java · Python · Spring Boot · Kafka · Kubernetes · Docker · REST · Linux · MongoDB ·

PostgreSQL · Azure · AWS · GCP · TCP/Netty · Grafana · Distributed Systems · High

Availability · Incident Analysis · Microservies · REST APIs

M.Sc. Computer Science - Technical University of Munich