Freelancer profile translated to English.
Back to original languageAbout Hassad
Backend developer, specializing in Go (Golang) on high-load distributed systems. About ten years in backend, with the last seven full-time on Go in production.
My specialty is large-scale performance and reliability: reducing latency on critical services, handling load on microservices architectures, smoothly evolving existing stacks.
I've worked on the real-time core of demanding platforms, from memory profiling and GC optimization to resilience patterns like circuit breakers, in sectors as varied as adtech, mobility, financial services, and data infrastructure.
I value architecture and performance equally: tested code, structured in hexagonal architecture and DDD, designed to last and remain easy to maintain. I've also designed my own SaaS products end-to-end, from the Go backend to the frontend, giving me a real product vision in addition to technical skills.
Before Go, I built industrial systems in Java and C++, which was excellent training for robust code and tight constraints.
Available for Go backend missions, from feature and API development to more specialized topics of performance and distributed architecture.
Main Stack: Go, Kubernetes, Kafka, gRPC, PostgreSQL, Redis, GCP, AWS
French
Native or bilingual
English
Native or bilingual
Can work on-site
Lyon (up to 50km)
Experience
- DatadogGo DeveloperSOFTWARE PUBLISHINGAugust 2025 - June 2026 (10 months)Go Backend Developer — Large-scale data infrastructureBackend development on large-scale data collection and processing infrastructure.Key achievements:• Go backend components for the metrics collection pipeline• Performance optimization: reducing memory allocations, profiling and GC tuning• Evolution of distributed storage systems (Cassandra, Kafka)• Implementation of resilience patterns: circuit breakers, backpressure, rate limiting• Internal observability: health metrics, tracing, alerting• Code review and technical documentation for knowledge transfer• Participation in incident debugging and runbook improvementStack: Go, Kafka, Cassandra, Redis, Kubernetes, Prometheus, OpenTelemetry, gRPC, Python
- QontoGo Backend DeveloperBANKING AND INSURANCEOctober 2024 - July 2025 (9 months)Paris, FranceBackend development for financial services aimed at professionals on the Qonto platform.Key achievements:• Go backend feature development on the main business application• Performance optimization: refactoring database queries, Redis caching• Evolution of the existing microservices architecture (Kafka, gRPC)• Interfacing with legacy Ruby on Rails for a gradual migration• Code review and pair programming on idiomatic Go patterns• Collaboration with product teams on technical specificationsStack: Go, Kafka, PostgreSQL, Redis, Kubernetes (EKS), Prometheus, Ruby on Rails
- CriteoGo Backend DeveloperPRESS AND MEDIAJune 2020 - May 2024 (3 years and 11 months)Paris, FranceLatency optimization on one of the world's largest advertising bidding engines (35 billion+ requests/day, decision in less than 10ms). Within the Core Bidding team, on the critical path of the real-time decision engine.Key achievements:• Hot path redesign: p95 latency reduction• Intensive memory profiling (pprof, escape analysis): reduced GC pressure, stabilized p99• Migration of the on-prem Kafka cluster to Confluent Cloud: cost -30%, producer throughput +45%• Adaptive circuit breakers for controlled degradation under heavy load• Mentoring junior developers and knowledge-sharing sessions (Go internals, distributed debugging)Stack: Go, Kubernetes (GKE), Kafka, gRPC, PostgreSQL, Redis, Prometheus, GCP
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Education
- Computer Science and Software Development Bachelor's DegreeUniversité Claude Bernard Lyon 12014Formation en développement logiciel : algorithmique et structures de données, programmation orientée objet, conception logicielle, bases de données relationnelles, systèmes et réseaux, génie logiciel. Fondations qui ont nourri une carrière orientée backend et systèmes distribués.