Freelance Data Engineer (Postgres / Systems Integration)

JUNI; Brandenburg; On-site; EUR 83,000 - 124,000; Part time

Job summary

JUNI is a Berlin-based non-profit science-startup ecosystem building a unified data layer across systems to a Postgres database. You will design bidirectional pipelines, resolve identity across sources, and ensure idempotent data flows while documenting decisions and enforcing data governance.

The role is freelance, starting as soon as possible, with Berlin or remote within the EU. You will collaborate asynchronously with a focus on robust, testable SQL and Git-driven migrations.

Qualifications

• Experience integrating third-party APIs with pagination, retries and signing.
• Bidirectional data synchronization with conflict resolution.
• Strong PostgreSQL experience including functions, triggers and RLS.
• Experience with data modeling and ETL pipelines.
• Excellent written English for async collaboration.

Responsibilities

• Design the data layer connecting diverse systems to a single PostgreSQL store.
• Ensure bidirectional sync with source systems and implement idempotent pipelines.
• Define schemas and pipelines; apply GDPR-conscious data handling.
• Write clear documentation and maintain Git-based migrations and reviews.

Skills

API integration

PostgreSQL

Data modeling

ETL pipelines

Idempotency

Git workflows

GDPR familiarity

English writing

Tools

Git

SQL

PL/pgSQL

Job description

About JUNI

JUNI is a non-profit science-startup ecosystem in Berlin. We run our programmes across seven SaaS tools — newsletter, events, community, CRM, forms, applications, coworking — and a Postgres database underneath that is meant to be the single place a person exists.
The database is the part we care about. One resolved record per person and per company, one append-only row per interaction, and a deterministic way of deciding which person a given payload belongs to. Its purpose is to make the path from first touchpoint to milestone measurable. The connective layer between the tools and that database is the work.

Your mission

Build the layer that connects our systems to one database, in both directions, and help us get the model right as we go.
The shape of the data is mostly decided, and each new system will test it. Sources disagree about what counts as one person, when something happened, and whether they'll tell you about it twice. Working that out — and knowing when the model has to change to accommodate a source, rather than being bent around it — is the substance of the job.
We're looking for someone who can think that through with us and make a case for a particular design, not only build what's specified.

Your profile

Scope
InboundEach system into the database. Several pipelines per system — sources report a lot of different things. Identity resolutionOutboundSome state originates with us rather than with a tool. The database decides and pushes to whichever platform executes it.Keeping both honestPlatforms report back and sometimes contradict us. Nobody who opted out may be re-added.ReportingKPI data has to reach a BI tool. Getting it there is part of the job; building the dashboards is not.SearchMaking the lake queryable in natural language.DocumentationDecisions written down, pipelines in github.
Not in scope

• Front-end. There is none and none is planned.

Required

• Integration against third-party APIs and webhooks, at depth: pagination, retries, signature verification, rate limits, undocumented payload shapes, late and out-of-order events, sources that fire on every change and won't say what changed.
• Bidirectional sync between systems that both think they own a field — loop prevention, echo suppression, an explicit answer to who wins on conflict.
• Postgres as an application database, not just a destination. plpgsql functions, triggers, constraints and RLS used to enforce rules at the write path. If your SQL experience is transformations downstream of the load, this is not the right fit.
• Idempotency as a habit rather than an afterthought. A pipeline that re-runs and changes nothing is the acceptance test.
• Git discipline — migrations, PRs, review.
• Working with personal data under GDPR, and understanding why that constrains what gets ingested at all.
• Written English. Most of the work is async, and what you build has to be legible to someone who wasn't there.

Useful, not required
n8n or another orchestrator Supabase relevance work on a search index — Elasticsearch, OpenSearch, Meilisearch or similar; cluster operations are not the part we need experience as the only person on a system German.

We offer

How we work
Remote and mostly async, but not silently so — expect real conversations, especially early, while you get your head around the systems and how they fit together.
Engagement
Freelance, starting as soon as possible. Three months to begin with; we'll see what's needed after that.
Berlin or remote within the EU.