Rust Grpc Services

# Rust gRPC Services with Tonic

## Objective

Build high-performance gRPC microservices in Rust using Tonic framework. The implementation must leverage Rust's zero-cost abstractions, memory safety, and concurrency primitives for maximum throughput and reliability.

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## Core Requirements

### Performance Targets

- **Latency**: p99 under 5ms for unary calls
- **Throughput**: 100,000+ requests/second per core
- **Memory**: Predictable memory usage with no garbage collection pauses
- **Concurrency**: Efficient async/await with Tokio runtime
- **Type Safety**: Compile-time guarantees for protocol correctness

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## Technology Stack

- **gRPC Framework**: Tonic v0.11+
- **Async Runtime**: Tokio v1.35+
- **Serialization**: Protocol Buffers (protobuf)
- **Database**: sqlx for PostgreSQL with compile-time query verification
- **Tracing**: tracing + tracing-subscriber for structured logging
- **Metrics**: prometheus-client for metrics export

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## Project Structure