Senior Python & Django Engineer

I design reliable backend systems
for complex, high-scale products.

Senior software engineer with 13+ years of experience building fintech, SaaS, and high-traffic platforms across Europe and Germany.

Based in Germany, working with distributed teams and critical business workflows.

View experience GitHub
13+
years experience
99.95%+
platform uptime
€100M+
revenue handled
Mounir Messelmeni - Senior Software Engineer

Core skills

Building backend platforms, integrations, and cloud-native systems that scale reliably.

Backend & architecture

Python Django DRF FastAPI Celery REST APIs OAuth2/OIDC Microservices API Design Domain-Driven Design

Data, messaging & integrations

PostgreSQL Redis Elasticsearch Kafka/MSK RabbitMQ EBICS Schema Registry Banking APIs

Cloud & delivery

AWS Kubernetes Docker Terraform GitLab CI/CD ArgoCD GitOps Observability

Frontend

React TypeScript Vite TanStack Query Orval Zustand Mantine UI Cypress Angular Tailwind CSS React Router Storybook

AI tooling & workflows

GitHub Copilot Claude Code OpenCode ChatGPT PI Pydantic AI LLM Integration AI Agent Workflows

Working style

  • Trusted by product, business, and engineering teams to drive decisions with clarity.
  • Comfortable in distributed teams, async communication, and cross-functional collaboration.
  • Brings calm, ownership, and follow-through in ambiguous or high-pressure delivery contexts.

Leadership

  • Helps teams align technical decisions with business goals and customer impact.
  • Mentors engineers and raises quality through pragmatic guidance and strong reviews.
  • Balances reliability and speed without compromising delivery standards.

Why teams hire me

I turn complex business processes into resilient systems that stay reliable under real load.

Delivery

Proven track record from startup scale-up to mission-critical fintech systems.

Reliability

Production systems built for uptime, observability, safe deployments, and rollback confidence.

Ownership

I design architecture, implement APIs, guide integration work, and raise engineering quality.

Experience

Building critical financial and SaaS platforms with measurable business impact.

02/2022 – Present

Senior Software Engineer

Payla Services GmbH

Remote, Germany

  • Defined service boundaries and backend architecture for a BNPL platform supporting roughly €100M annual revenue, €270M shipments, and €350M requested orders with 99.95%+ uptime.
  • Designed EBICS/CAMT53 banking integrations and SEPA direct debit/credit transfer workflows, streaming parsed transactions through Kafka/MSK into reconciliation and financial-processing services.
  • Built AWS/Kubernetes microservices using synchronous REST APIs and event-driven Kafka/RabbitMQ communication with PostgreSQL-backed workloads and production-grade reliability controls.
  • Established GitOps delivery with GitLab CI, Argo Workflows, ArgoCD and Kubernetes, including automated testing, compatibility validation, and progressive rollouts with rollback protection.
  • Led OAuth2/OIDC architecture using Ory and Django OIDC libraries with centralized permission mapping and infra-as-code identity sync.

02/2015 – 01/2022

Senior Software Developer

RegioHelden GmbH

Stuttgart, Germany

  • Designed and evolved a Django-based invoicing, payment-management, reconciliation, and dunning platform supporting more than €180M in invoiced payment flows.
  • Implemented financial workflows for invoice generation, direct debit, recurring billing, payment matching, dunning, and accounting exports using Python/Django, PostgreSQL, scheduled jobs, and EBICS/SEPA integrations.
  • Led the migration from Python 2 to Python 3, including compatibility testing, Celery serialization updates, and dependency evaluation without disrupting delivery.
  • Modernized a legacy Django/AngularJS platform with REST-driven APIs and Angular SPA components, improving maintainability while preserving compatibility.
  • Mentored junior developers and acted as a technical contact for complex engineering issues.

01/2013 – 02/2015

Python/Django Engineer

3B Enterprise

Tunis, Tunisia

  • Designed and operated the Django backend for Keejob.com, a recruitment platform serving ~2 million monthly page views using PostgreSQL, Redis, RabbitMQ, NFS, and load-balanced app servers.
  • Built job publishing, search, applications, notifications, and analytics services with asynchronous and scheduled processing through Celery/RabbitMQ.
  • Established automated testing, caching, performance practices, and automated deployment with Ansible and GitHub Actions.

Education

Engineer Diploma in Software Engineering

National Institute of Applied Science and Technology (INSAT), Tunis

Languages

  • English: Advanced
  • French: Fluent
  • German: B1 certified, spoken B2

Why Choose Me?

10+ years of experience turning complex challenges into elegant solutions

Fast Delivery

Agile development with rapid prototyping and iterative delivery

Secure & Scalable

Enterprise-grade security and built to scale with your business

Custom Solutions

Tailored software solutions that fit your unique business needs

Selected projects & open source

A few personal projects and public contributions that reflect how I build and ship real-world software.

Own projects

Own repo

htmxango

+

Django + HTMX experiments that show how I build modern server-rendered interfaces without unnecessary frontend complexity.

Django HTMX Python
Open on GitHub →
Own repo

drf-idempotencykey

+

Reusable idempotency-key support for Django REST Framework, aimed at safe retries and payment-facing API robustness.

DRF API Design Python
Open on GitHub →
Own repo

jobfit

+

Multi-agent job-fit evaluator using Pydantic AI and Ollama, demonstrating my interest in modern LLM-driven product tooling.

Pydantic AI Ollama Python
Open on GitHub →
Own repo

django-highlightjs

+

A Django package for integrating Highlight.js cleanly into templates and admin-facing UI.

Django Python Open Source
Open on GitHub →
Community

Public contributions

+

Latest Blog Posts

Recent writing on Django migrations, Kafka, and resilient backend systems

Django

Django Migrations

Django-Syzygy: Safe Zero-Downtime Database Migrations

A practical guide to making database migrations safer during rolling deployments, especially in production environments with live traffic.

Jan 16, 2026 Read More →

Kafka

Kafka Architecture

Understanding Apache Kafka: A Beginner's Guide to Partitions, Consumers, and Migrations

Learn the core building blocks of Kafka, from partitions and consumer groups to handling tricky topic migrations in real systems.

Jul 25, 2025 Read More →

Deployment

Django DevOps

Zero Down Time DB migrations with Django

Practical advice for avoiding downtime while shipping schema changes in Django, with a focus on production-safe rollout patterns.

Jul 2, 2025 Read More →
Visit My Blog

Let’s build the next reliable platform.

I’m available for senior backend, platform, and engineering leadership roles across product and fintech teams.

Email

messelmeni.mounir@gmail.com

GitHub

/mounirmesselmeni

LinkedIn

/in/mounirmesselmeni
Contact me