Job Title: Lead Ruby Developer
Experience Required: 12+ years
Assignment Duration: 12+ Months
Engagement Type: Contract
Work Location: Chicago, IL
Client: Fujistu
send resume at [Upgrade to PRO to see contact]
please update resume according to the JD
Key Responsibilities & Required Technical Expertise:
Strong Expertise with Ruby:
* Minimum 12 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
o sub-50ms API latency under load
o High throughput using connection pooling, query batching
* Hands-on tuning:
o Puma workers vs threads trade-offs
o 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