Senior Java Software Developer / Mass Data Backend Engineer

Project overview

For our client from the public sector, we are looking for a Senior Java Software Developer / Mass Data Backend Engineer (m/f/d) starting immediately.

+++Important: Deadline for feedback is Thursday 1 PM+++

Responsibilities

• Development of the mass data pipeline: Design and implementation of robust, stateless microservices for receiving, pre-processing, and persisting millions of daily transactions.
• Format Parsing & Validation: Building streaming parsers and validation engines for structured e-invoicing formats (EN 16931, XRechnung, Peppol BIS Billing, XML/UBL, JSON) with minimal memory footprint.
• Event Streaming & Caching: Conception and implementation of asynchronous messaging and streaming routes (e.g., via Apache Kafka) as well as efficient caching and buffering mechanisms.
• Data Storage & Persistence Design: Co-designing partitioning, sharding, and indexing strategies for relational and distributed database systems (PostgreSQL / NoSQL / Time-Series/Mass Data Stores).
• Performance Engineering & Load Testing: Continuous performance analysis, profiling (memory, CPU, I/O bottlenecks), concurrency optimization, and execution of automated load tests.
• Quality Assurance & Security: Creation of automated unit tests, integration tests (Testcontainers), and implementation of strict security requirements (BSI IT-Grundschutz, TLS/mTLS, encryption at rest/in transit, tax secrecy § 30 AO).
• Collaborative Work: Active participation in the agile team (Scrum), close technical coordination with colleagues.

Requirements

Skills:

• At least 5 years of demonstrable practical experience in professional software development with Java in an enterprise environment.
• Demonstrable project experience in processing mass data / high-throughput systems (batch and streaming processing).
• Solid practical experience in conception and development with Apache Kafka (Consumer Groups, Partitioning, Offsets, Schema Registry) or comparable message brokers. Experience with REST interfaces.
• Very good knowledge of the Spring ecosystem (Spring Boot 3, Spring Batch, Spring Data).
• Comprehensive experience in data modeling, index optimization, connection pooling, and transaction control in relational databases (e.g., PostgreSQL) under high load.
• Proven practical experience with Docker/Podman and deployment on Kubernetes or Red Hat OpenShift.
• Very good knowledge of JUnit 5, Mockito, and Testcontainers for isolated testing of databases and message brokers.
• Fluent German and English, spoken and written (at least language level C1 in German and B2 in English).
• E-invoicing Standards: Practical experience with XML/XSD validation, Schematron, CEN/TC 434, EN 16931, XRechnung, or Peppol.
• Distributed Storage & Caching: Experience with NoSQL data stores, document stores, or in-memory data grids (e.g., Redis, Infinispan).
• Resilience & Monitoring: Experience with circuit breakers (Resilience4j) and observability tools (OpenTelemetry, Prometheus, Grafana).
• Public Sector / Taxes: Knowledge of KONSENS architecture standards, tax administration procedures, or governmental BSI security requirements.
• Agile Working: Experience in cross-country or inter-agency agile development projects (Scrum / SAFe).

Project details

asap

12 months +

Full-time

90% Remote - Frankfurt

+++Willingness for a SÜ2 clearance must be given+++

• Start: ab sofort
• Duration: 12 Monate
• Remote: hybrid
• Location: Frankfurt, Deutschland, DE
• Languages: German