Senior Java Engineer

Data & Event Systems — SimX Platform

Full-Time | Remote (Egypt) | Contractor

About Telkoa

Telkoa builds SimX, a SIM and eSIM management platform for telecom operators. We process millions of SIM lifecycle events, network signaling messages, and usage records daily across multiple cloud environments (Hetzner K3s, AWS EKS, VMware on-prem), serving telecom operators in Europe, Latin America, and Southeast Asia.

SimX is a data-intensive platform at its core. Real-time Kafka event streaming, CDC pipelines, time-series aggregation, and geospatial analytics are central to everything we do. We are a small, senior team that ships fast. No layers of management, no ticket factories.

The Role

We are looking for a Senior Java Engineer to own the data backbone of SimX. This is not a generic backend role — the core of your work is designing and operating real-time Kafka event pipelines, CDC-driven data flows, time-series aggregation, and high-throughput batch processing that telecom operators depend on 24/7.

SimX processes millions of SIM lifecycle events daily through a Confluent Kafka ecosystem with Avro schemas, ksqlDB stream enrichment, Debezium CDC, and Kafka Connect. Data lands in PostgreSQL with TimescaleDB hypertables, PostGIS geospatial extensions, and custom aggregation pipelines driven by pg_cron. You will build and operate these systems.

What You Will Work On

Kafka Event Streaming & CDC Pipelines (~40%)

- Design and operate Kafka-based event streaming pipelines for real-time SIM provisioning, IMSI swaps, and network signaling across multiple operator networks. The platform uses Confluent Platform with Avro serialisation and Schema Registry.

- Build and maintain Debezium CDC connectors that capture PostgreSQL changes and route them to Kafka topics for downstream enrichment and processing.

- Work with ksqlDB to build stream enrichment pipelines — joining raw event streams with subscriber data to produce enriched topics consumed by downstream services.

- Configure and maintain Kafka Connect JDBC sink connectors that write processed data back to PostgreSQL.

- Design data flow architectures that ensure reliability, ordering guarantees, and exactly-once processing across distributed services.

Database Engineering & Aggregation (~25%)

- Design and optimise PostgreSQL schemas for high-volume transactional and analytical workloads. SimX uses raw SQL throughout — no JPA/Hibernate.

- Work with TimescaleDB hypertables for time-series data (event records, quality-of-service aggregations) including retention policies, chunk management, and query optimisation.

- Build and maintain aggregation pipelines using pg_cron — hourly and daily rollups that transform raw telemetry into operator-facing analytics (the qmax pipeline is the centre of gravity).

- Implement and optimise geospatial queries using PostGIS and Uber H3 hexagonal indexing for location-based analytics and geofencing.

- Design and manage multi-tenant data isolation using PostgreSQL Row-Level Security (RLS), with per-deployment access policies.

Batch Processing & Data Operations (~20%)

- Build and maintain batch processing systems for usage aggregation, billing reconciliation, SIM inventory operations, and large-scale data migrations.

- Design ETL/ELT pipelines for data transformation, enrichment, and loading across operational and analytical stores.

- Implement data quality checks, validation rules, and automated error remediation for high-volume batch jobs.

- Manage schema evolution across Avro schemas, PostgreSQL DDL, and ksqlDB streams in a coordinated manner.

API Services & Architecture (~15%)

- Contribute to SimX's Java Spring Boot microservices — REST APIs consumed by telecom operators for SIM management, provisioning, and analytics.

- Make architectural decisions on system design, service decomposition, and data modeling for a platform deployed across Hetzner (K3s), AWS (EKS), and VMware (on-prem K8s).

- Establish engineering patterns, code review standards, and mentor a mid-level engineer.

Requirements

Must Have

- 4–6 years of production experience with Java and Spring Boot. SimX is 90% Java Spring Boot microservices — this is not negotiable.

- Hands-on experience with Apache Kafka in production — topics, consumers, producers, consumer groups. Experience with the broader Confluent ecosystem (Schema Registry, Kafka Connect, ksqlDB) is a major advantage.

- Strong PostgreSQL skills with real experience writing and optimising raw SQL at scale. SimX does not use JPA or Hibernate — you will write SQL directly, design schemas, tune queries, and manage migrations.

- Experience with data aggregation pipelines — batch rollups, materialised views, scheduled processing jobs that transform raw event data into analytics.

- Experience with CDC (Change Data Capture) patterns — Debezium or equivalent tools that replicate database changes to event streams.

- Experience with containerised deployments — Docker, Kubernetes (K8s or K3s), Helm charts.

- Ability to work autonomously with minimal supervision. We are async-first and remote.

- Strong written English for async communication, code reviews, and documentation.

Strong Plus

- TimescaleDB — hypertables, retention policies, chunk management for time-series data.

- PostGIS or geospatial database experience.

- Avro schema design and evolution in a Schema Registry environment.

- Experience with ksqlDB or Kafka Streams for real-time stream processing.

- Telecom domain knowledge — SIM/eSIM, IMSI, network signaling protocols, OTA provisioning.

- Multi-tenant database design using Row-Level Security or equivalent isolation patterns.

- Proficiency with AI-assisted development tools (Claude Code, Cursor, GitHub Copilot) — we value engineers who use AI to multiply their output.

- Familiarity with GitLab CI/CD pipelines.

How We Work

- Tools: Linear (project management), GitLab (code + CI/CD), Outline (knowledge base), Slack (communication).

- Process: Issues tracked in Linear. Agile but lightweight — no ceremonies for the sake of ceremonies.

- Cadence: Async-first. Weekly sync with the CEO/CTO.

- Compensation: Competitive monthly rate (USD), contractor agreement, monthly invoicing.

Why This Role

You would own the data layer of a platform that telecom operators depend on in production. This is not CRUD APIs — it is real-time CDC pipelines, Kafka event streaming with Avro and ksqlDB enrichment, TimescaleDB aggregation at scale, and geospatial analytics across distributed operator networks. The problems are hard, the data volumes are real, and your architectural decisions will shape the platform for years.

You will work directly with the CEO/CTO — no layers of management between you and the decisions that matter. The telecom data space is underserved by modern engineering, and you would be building capabilities that most platforms in this industry simply do not have.

To apply: careers@telkoa.com

Application Question(s):

• How many years of production experience do you have with Java and Spring Boot?
• Describe your experience with Apache Kafka in production. Include specifics: throughput, number of topics, consumer groups, and whether you've worked with any of the following: Confluent Schema Registry, Avro, ksqlDB, Kafka Connect, or Debezium CDC.
• Describe your PostgreSQL experience at scale. Have you worked with raw SQL (not JPA/Hibernate), query optimisation, sharding, partitioning, or time-series extensions like TimescaleDB?
• Describe a data pipeline or batch processing system you built that handled high volumes (millions of records). What was the architecture, what challenges did you face, and how did you solve them?
• What tools do you use to multiply your engineering output? Do you use AI-assisted development tools like Claude Code, Cursor, or GitHub Copilot? If yes, describe how you use them in your workflow.
• Do you have any experience in the telecom domain — SIM/eSIM, IMSI, OTA provisioning, network signaling, or working with telecom operators?
• What is your expected monthly compensation in EGP?
• What is your notice period at your current role?
• Are you comfortable working fully remote and async-first, communicating primarily in English with a globally distributed team?

Work Location: Remote