Senior Python (FastAPI) Developer - Remote - Freelance

Context

We are supporting a fast-growing tech scale-up operating an e-commerce / marketplace model with strong operational constraints around device replacement.

Business objective:
Accelerate defective device replacement cycles and maintain a customer delivery time under 7 days.

Technical challenges:

• Scaling services handling ~70+ orders per day (and growing)

• Event-driven architecture with Kafka

• High availability and resilience

• Real-time monitoring and alerting (Datadog)

• Performance optimization across distributed microservices

Current environment:
Python 3.11 + FastAPI, Kafka (Confluent), Datadog, Azure & GCP (Cloud Run / Azure Functions), Docker, GitHub Actions CI/CD, PostgreSQL, Redis.

Roadmap:

• January: Architecture finalization & implementation kickoff

• End of February: MVP delivery

• Q2: Scaling phase & performance hardening

Team setup:

• 3 Backend Engineers

• 1 Frontend Engineer

• 1 Tech Lead (50% backend)

• Agile Scrum (Slack, Jira, GitHub)

Responsibilities

• Design and implement the device replacement API, including Kafka event integration.

• Improve microservices performance (latency reduction, throughput optimization).

• Ensure high availability and fault tolerance across services.

• Implement structured monitoring & alerting with Datadog (APM, logs, dashboards).

• Write and maintain unit and integration tests (pytest).

• Contribute to CI/CD improvements (GitHub Actions).

• Participate in architecture decisions and technical design reviews.

• Conduct code reviews and mentor junior engineers.

• Document APIs, internal processes, and operational runbooks.

• Contribute to scalability strategy for Q2 growth phase.

Technical Stack

• Backend: Python 3.11, FastAPI

• Architecture: Microservices, event-driven

• Messaging: Kafka (Confluent)

• Cloud: Azure Functions, GCP Cloud Run

• Databases: PostgreSQL, Redis (caching)

• Monitoring: Datadog (APM, logs, alerts)

• DevOps: Docker, GitHub Actions CI/CD

• Testing: Pytest

Profile Required

• 7+ years of experience in Python backend development.

• Strong production experience with FastAPI (or similar async frameworks).

• Proven experience with Kafka and event-driven architectures.

• Experience working in scale-ups or unicorn environments (high velocity, strong engineering standards).

• Strong knowledge of distributed systems, scalability and resilience patterns.

• Solid understanding of cloud environments (Azure and/or GCP).

• Experience with CI/CD pipelines and automated testing.

• Comfortable working in small, autonomous teams.

• Fluent English (mandatory).

• Strong communication skills and ownership mindset.

Conditions

• Freelance contract (6 months, renewable).

• Full remote.

• Candidate must be based in France or Spain.

• Monthly deliverables with performance KPIs.

• Direct collaboration with product and engineering leadership.

• Access to internal tools (Slack, Jira, GitHub).