Senior Java ETL Data Engineer

Senior Java ETL Data Engineer

3E · Brussels, Belgium (Hybrid) · Full-time · Posted 2026-09-10

Workplace: hybrid

Department: Products

Description

Our SynaptiQ platform collects near-real-time data from more than 20 million devices across thousands of utility-scale solar and wind sites worldwide. Everything the platform does — the analytics, the alarming, the reporting our clients run their portfolios on — depends on that data arriving complete, on time and correctly normalised. To keep that foundation solid as the portfolio grows, we are looking for a Senior Java ETL Data Engineer to own the technical direction of the engine that makes it happen.

You will join our Product Engineering organisation, working in a small cross-functional team of 2–3 engineers and reporting to an Engineering Manager. You will work closely with Product Management to define both what gets built and how it is implemented, and with Operations when things break. The working language is English. Day to day you will be in high-performance Java, S3-compatible object storage (S3, ABS, GCS), streaming infrastructure, and Linux.

This is a senior individual contributor role. You will own the ETL engine — not a slice of it - and day-to-day:

• You design, develop and operate the Java ETL engine that processes near-real-time data from millions of renewable energy assets. Ownership here runs from conception through to production operation: you build it, you run it, you fix it.
• You architect and integrate the engine with S3-compatible object storage and streaming infrastructure. Deciding how and when we adopt a given storage or streaming technology is your call to make and justify.
• You balance the technical trade-offs between real-time and batch processing, and make those calls on evidence rather than preference.
• You take the lead on quality and reliability through code review, testing and SRE practice — including incident response and postmortem analysis when something goes wrong at 2am on a Sunday.
• You decompose pipeline problems into actionable milestones and plans, so the team knows what "done" looks like before work starts.
• You maintain the architecture decisions, runbooks and API documentation that let the rest of us operate what you build.

Requirements

We are looking for someone who takes an idea all the way to production and stays with it afterwards. Someone technically rigorous, who writes high-performance concurrent Java and genuinely cares how systems behave under load at three in the morning. And someone pragmatic — who knows when to ship and when to slow down and do it properly. To qualify as our ideal candidate:

• You have 7+ years of software engineering experience, including at least 3 years writing and operating high-performance Java in production.
• You have a deep understanding of Java concurrency, parallelism and performance optimisation. This is the core of the job — the engine handles millions of devices, and naive code does not survive contact with that volume.
• You have hands-on experience with data processing pipelines on S3-compatible object storage, and you are comfortable with Linux system administration.
• You have delivered and operated production systems end-to-end — code review, testing, monitoring, incident response.
• You are an architectural thinker. You evaluate technologies on evidence and guide the team toward sound choices rather than fashionable ones.
• You hold a Master's in Computer Science, Engineering or equivalent by experience.
• You speak and write fluent English. It is our working language across engineering.
• You can work autonomously: we don't have a micromanagement culture around here. Processes are light and we expect you to find information independently, ask for help when you need it, and improve the process rather than wait for one.
• You can explain a technical trade-off to someone who isn't an engineer — Product and Operations need to understand the consequences of your decisions to make their own.

Bonus points for

• Streaming platforms — Kafka, Flink or Pulsar
• Time-series databases
• Renewable energy sector experience

Benefits

Our offices are hidden in the centre of Brussels with a view on a pond, with ducks and a heron bringing a regular visit. In addition to a stimulating atmosphere in a highly motivated group of people, 3E offers a unique opportunity to further develop yourself in a company/team with an ambitious growth plan, delivering innovative services.

Furthermore:

• Training on the job by our experts so you get to know our solution and work in and out
• Flexibility, responsibility and freedom in your day-to-day work.
• An international environment with projects in over 100 countries worldwide, colleagues of over 20 nationalities.

We are open to both independent contractors (commitment to 219 invoiced days/year) or payroll contracts. For a Belgian payroll contract, the extralegal benefits are:

• Home working (2 days per week)
• Hospitalisation insurance
• Pension saving
• Representation allowance
• €9 meal voucher/day
• flexible income plan
• 20 legal days off + 12 compensation days (per full year worked)
• sustainable transport subscription and/or bike allowance (€0.36/km).

Apply

Apply at 3E

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