Senior Ruby Developer 

Experience Required: 12+ years
Assignment Duration: 12+ Months
Engagement Type: Contract
Work Location: Chicago, IL

Rate: $45-50/Hr C2C

Key Responsibilities & Required Technical Expertise:

Strong Expertise with Ruby:

• Minimum 8 years of experience on Ruby
• Deep knowledge of Ruby MRI internals (GIL, memory model, object
• allocation)
• Ruby MRI garbage collector (mark & sweep, generational GC)
• Strong experience with Rails internals (ActiveRecord, Arel, middleware
• stack)
• Ability to optimize slow queries, N+1 issues, and memory leaks
• Experience with multi-threaded / concurrent Ruby (Puma, Sidekiq tuning)
• Ruby VM instruction set (YARV bytecode basics)
• Concurrent Ruby gem
• Thread pools vs Fibers vs Ractors
• Async frameworks (Falcon / Async gem)
• Experience integrating Ruby with Kafka (ruby-kafka / Karafka), exactly-once
• semantics handling
• Designing: event schemas, schema evolution (Avro / JSON schema)

Proven experience scaling Rails apps to:

• 10K+ RPS
• millions of daily transactions
• Hands-on experience with:
• Event-driven architecture (Kafka / RabbitMQ)
• CQRS & Event Sourcing
• Saga pattern (choreography & orchestration)

Strong understanding of:

• Eventual consistency
• Distributed transactions
• Idempotent APIs

Deep understanding of:

• Caching strategies (Redis, Memcached)
• Background processing (Sidekiq, Resque)
• Database sharding and read replicas

Strong experience with:

• PostgreSQL (query tuning, indexing, vacuum, locking)
• Redis (data structures, pub/sub, distributed locks)

Ability to debug:

• deadlocks
• slow queries
• replication lag
• Low-Latency / High-Throughput Optimization

Experience achieving

• sub-50ms API latency under load
• High throughput using connection pooling, query batching
• Hands-on tuning:
• Puma workers vs threads trade-offs
• kernel tuning (ulimits, TCP tuning)

Deep Sidekiq Internals:

• Queue prioritization strategies
• Dead job recovery
• idempotent job design
• Redis contention debugging
• Sidekiq middleware customization

Experience with:

• AWS (EKS, RDS, SQS, Lambda)
• Docker & Kubernetes
• CI/CD pipelines (GitHub Actions / Jenkins)
• Observability stack:
• o Prometheus
• o Grafana
• o ELK / OpenSearch
• OAuth2 / JWT authentication
• PCI-DSS exposure (preferred)
• Secure API design (rate limiting, mTLS, encryption)
• Experience working at:
• * high-frequency trading firms
• * payment processors
• * crypto exchanges
• * JRuby / TruffleRuby
• * GraphQL APIs
• * gRPC services
• Exposure to:
• * fraud detection systems
• * real-time risk engines