Toptal: Senior SQL Developer

About the Client

Our client is a well-established healthcare technology and services organization specializing in workforce management, payroll, and compliance solutions for regulated environments.

We are seeking a Senior SQL Developer (Performance Optimization) to diagnose, optimize, and stabilize a high-volume SQL environment supporting thousands of concurrent users. The primary focus is improving slow-running queries, resolving locking and blocking issues, tuning Entity Framework–generated SQL, and optimizing reporting workloads within a C#/.NET and Angular application stack.

General Information

The client operates a large-scale, real-time system where users continuously log timesheets, trigger background processes, and generate reports. The backend relies heavily on SQL with Entity Framework, while multiple background jobs and reporting workflows run concurrently throughout the day.

Due to growing data volume and concurrency, several SQL queries, stored procedures, and EF-generated queries are performing slowly or causing locks. The goal is to bring in an expert who can conduct a full performance audit, rewrite or tune problematic queries, and improve system reliability and responsiveness.

Tasks and Deliverables

• Conduct a full performance audit of existing SQL queries, stored procedures, and reporting pipelines

• Optimize slow-performing queries, multi-table joins, window functions, and EF-generated SQL.

• Diagnose and resolve locking, blocking, and deadlock conditions

• Improve indexing strategy, query plans, and concurrency handling

• Optimize Entity Framework usage patterns and reduce unnecessary DB roundtrips

• Review and optimize SQL interactions within API calls and background jobs

• Implement monitoring to track query health, performance regressions, and long-running jobs

• Provide documentation and knowledge transfer to internal engineering leadership

Additional Details

• Location: Ramapo, New York, United States (US-based talent only)
• Type: Full-time 40h/week Contract
• Work model: Hybrid – 2-3 times/week in office
• Duration: 3–6 months with potential extension
• Authorization: Applicants must be authorized to work in the US without employer sponsorship

Required Experience

• Expert-level SQL skills with proven experience optimizing complex queries at scale

• Strong experience with locks, blocking, deadlocks, and concurrency patterns

• Hands-on experience tuning stored procedures, CTEs, and window functions

• Experience with C#/.NET and Entity Framework performance tuning

• Familiarity with high-concurrency systems and background job processing

• Experience working with SQL performance tools (Query Store, Profiler, Execution Plans)

Nice to Have

• Experience optimizing large reporting workloads

• Familiarity with Angular-based frontend environments

• Experience scaling systems with thousands of concurrent users

• Experience with ETL pipelines or job schedulers in .NET ecosystems