Sébastien Lemeur

Contribution to a collaborative last-mile delivery platform between merchants and individuals. The solution relies on a mobile application and a set of backend APIs. The team consists of approximately 20 developers, ops, and SREs. Within the backoffice, KYC, and delivery APIs in TypeScript: development of a complete dispute management mechanism, implementation of co-carrier moderation rules, and integration of third-party services via webhooks and event-driven workflows. Data storage across several PostgreSQL databases, cache management via Redis, and indexing across several Elasticsearch databases for efficient searches on deliveries and co-carriers. The architecture adheres to the Hexagonal model (ports/adapters) and Clean Code principles, with complete testability (unit, integration, and acceptance tests). A strong observability culture is applied across all services (structured logs, metrics, traces). Services are deployed on Kubernetes (ingress migration to Gateway API, ArgoCD orchestration), infrastructure is managed via Terraform IaC, and CI/CD is implemented with GitHub Actions. Production environments are actively monitored via an APM to ensure performance, reliability, and rapid incident detection.

Development of a large-scale, event-driven solution enabling station agents and carriers to manage passenger information and disseminate it across all stations in France and internationally.

Development of a frontend in React (TypeScript) and a backend based on a monorepo of AWS Lambda functions (Node.js/TypeScript) and Kubernetes containers, divided into business components. Data storage on PostgreSQL and DynamoDB. Implementation of event-driven communication via ActiveMQ, Amazon SQS, and DynamoDB Streams. The architecture adheres to the Hexagonal model (ports/adapters) and Clean Code principles, with complete testability covering code (unit, integration, and acceptance tests) as well as infrastructure (load and resilience tests). The infrastructure is managed via Terraform IaC, and CI/CD is implemented with GitLab and Jenkins. Production environments are actively monitored with Datadog to ensure performance, reliability, and rapid incident detection.

Development of a SaaS solution for managing invoices for several thousand clients with a team of 20 developers. Implementation in TypeScript of an Angular frontend and a NestJS API, adhering to Hexagonal Architecture, DDD principles, and the CQRS pattern. Deployment of an event-driven architecture based on RabbitMQ for invoice processing. Implementation and management of unit, integration, and acceptance tests, designed according to Gherkin principles with CucumberJS and Playwright. Implementation and management of continuous integration and deployment via GitLab, as well as monitoring of development and production environments with Grafana and Prometheus to ensure system health, performance, and availability.