Backend Performance Tuning: SQL/NoSQL Query Optimization & API Diagnostics (Java / .NET)

We need a developer to improve backend performance for an existing application by optimizing database queries and diagnosing API bottlenecks. The work includes analyzing slow queries, identifying inefficient data access patterns, and recommending practical improvements to reduce response times and improve reliability. You should be comfortable working with both SQL and NoSQL systems and be able to document findings clearly. This is a part-time project for someone who can quickly assess performance issues and help implement measurable improvements.