Python Developer

Senior Python Engineer

About the role

We run a distributed, camera-based video monitoring and AI alerting platform. The estate

spans an AWS-hosted fleet of services and workers, a GPU-backed computer-vision inference

pipeline, a real-time streaming and presence layer, and thousands of on-premise edge "media

boxes" that ingest camera feeds, serve video, and stream events back to the cloud.

Today the bulk of our backend is ~140 Java 8 services and libraries that have grown over

many years. We are building their successor: a clean, modern Python monorepo (trella), and

we are migrating capabilities over to it service by service.

We are looking for a Senior Python Engineer: a strong programmer first, with real depth in

both Python and Java to lead and execute that migration. You will design and build the new

Python services, port existing Java functionality across with its behaviour intact, and

occasionally maintain and fix the existing Java stack while it remains in production. This

is a builder's role at the centre of a major platform modernization.

What you'll work on

The new Python platform (primary)

A greenfield, strongly-opinionated monorepo built for the long term:

• Python 3.14, managed with uv workspaces (libs/, packages/, svcs/, apps/, scripts/), scaffolded from Copier templates.
• FastAPI services with Strawberry GraphQL as the primary data API; REST where it's the right fit; Uvicorn ASGI. psycopg3 straight against PostgreSQL / TimescaleDB using the repository pattern deliberately no ORM — with yoyo migrations.
• Pydantic / pydantic-settings for models, validation, and config; httpx for outbound
• HTTP; pendulum for datetimes; structlog + OpenTelemetry for observability.
• Strict engineering standards, enforced in CI: full type annotations under a strict mypy config, ruff lint + format, and a curated, opinionated set of approved libraries (alternatives are banned at the linter level, on purpose).
• A strong testing culture: pytest, TestClient, async tests, real test databases.

The legacy Java stack (occasional, ongoing)

• ~140 Java 8 services and libraries: REST APIs, SQS/SNS workers, Lambda functions built with Gradle and Bazel, running on Jetty 9.4, deployed to Elastic Beanstalk, ECS, and Lambda.
• Domains include alerts, analytics, API, auth, clips, media, presence, notifications, and partner integrations.
• You'll read this code to understand behaviour before porting it, keep it healthy with bug fixes and small changes while it's still live, and decommission pieces as their
• Python replacements land.

The platform around it

• AWS (us-west-2): EC2/ECS, Lambda, S3, RDS (PostgreSQL/TimescaleDB),
• ElastiCache (Redis), MSK (Kafka), Kinesis & Kinesis Video Streams, IoT Core, Cognito, SQS/SNS/SES.
• A GPU-backed computer-vision inference tier producing the alerts that reach parents' phones.
• Edge appliances (Linux + Docker) in the field, reachable over AWS IoT.

What you'll do

• Design and build new Python services in the monorepo (schema, data access, business logic, APIs, and tests) to a high, consistent standard.
• Migrate functionality from Java to Python: study an existing Java service, capture its real behaviour and edge cases, and re-implement it idiomatically in Python without regressions.
• Maintain the Java stack as needed: diagnose and fix production issues, make targeted changes, and keep services healthy until they're retired.
• Set and uphold engineering standards in the new codebase: typing, structure, the libs/svcs separation, the repository pattern, testing, and review quality.
• Work with data: model schemas in PostgreSQL/TimescaleDB, write correct and efficient SQL, and design migrations.
• Own your work end to end: from design through deploy, observability, and on-call follow-through, and drive it to a durable resolution.

Required qualifications

• Strong software engineer first. Excellent fundamentals: data structures, concurrency,
• API and data modelling, testing, and writing code others can maintain.
• Senior-level Python in production: idiomatic, fully typed, well-tested. Comfort with
• async, packaging, and a modern toolchain (type checkers, linters, virtual envs).
• Solid Java in production: able to confidently read, debug, and modify a large existing
• Java codebase, and reason about its behaviour well enough to port it.
• Strong with relational databases (PostgreSQL preferred) writing SQL directly rather than leaning on an ORM, and designing schemas and migrations.
• Hands-on AWS experience building and operating real services.
• Migration / modernization mindset: you can hold "match the old behaviour" and "build it right for the next ten years" in your head at the same time.
• A bias for follow-through: you find what's actually needed, focus on it, and finish.
• Excellent English communication.

Nice to have

• FastAPI, GraphQL (Strawberry or similar), and async Python at scale.
• uv, monorepo workflows, and strict typing (mypy) / ruff in CI.
• TimescaleDB or other time-series data.
• Gradle and/or Bazel builds; Jetty; AWS Lambda.
• Messaging and streaming: Kafka/MSK, SQS/SNS, Kinesis.
• Containers (Docker/ECR/ECS), CircleCI, and infrastructure-as-code (Terraform).
• Auth with Cognito, JWT/OIDC, or Entra; partner-integration work.
• Computer-vision / ML-adjacent systems, IoT, or edge/on-premise fleets.

How we work, and what we expect

• Prefer the right fix to a quick patch. Solve the root cause; don't paper over it.
• Follow-through over activity. We measure outcomes, not hours. Work is driven to a correct, durable resolution on a reasonable timeline, not left half-done.
• Standards are not optional. The new codebase is opinionated by design; we keep it clean, typed, and tested so it stays fast to work in.
• Respect what exists before you replace it. Understand the Java behaviour you're porting; migrate deliberately, with tests, and decommission cleanly.

Why this role is interesting

You will own the migration of a mature, real product from a large legacy Java estate to a

clean, modern Python platform, making the architectural calls, setting the standard for

everything that follows, and seeing your work reach a camera on a wall, an AI model, and a

notification on a parent's phone. You get the satisfaction of greenfield Python without losing

the grounding of a system that's already in production.

We are an equal-opportunity employer. We welcome applicants from all backgrounds and are

committed to building an inclusive team.

Requirements for the Interview

• The candidate should be able to complete 3 exercises in Python, version at his choice.
• Have setup ready to code. We don't want live code IDE.
• Good communication.