2025-08-23 14:35:27 +03:00
6 changed files with 651 additions and 10 deletions
--- a/README.md
+++ b/README.md
@ -0,0 +1,87 @@
+# Hash of Wisdom
+
+A TCP server implementing the "Word of Wisdom" concept with proof-of-work challenges to protect against DDoS attacks.
+
+## Overview
+
+The Hash of Wisdom server requires clients to solve computational puzzles (proof-of-work) before receiving wise quotes. This approach prevents spam and DDoS attacks by requiring clients to invest CPU time for each request.
+
+## Quick Start
+
+### Prerequisites
+- Go 1.24.3+
+- Docker (optional)
+
+### Building
+```bash
+# Build server
+go build -o hash-of-wisdom ./cmd/server
+
+# Build client  
+go build -o client ./cmd/client
+```
+
+### Running
+```bash
+# Start server (uses config.yaml by default)
+./hash-of-wisdom
+
+# Or with custom config
+./hash-of-wisdom -config /path/to/config.yaml
+
+# Connect with client
+./client -addr localhost:8080
+```
+
+### Using Docker
+```bash
+# Build image
+docker build -t hash-of-wisdom .
+
+# Run container
+docker run -p 8080:8080 -p 8081:8081 hash-of-wisdom
+```
+
+### Monitoring
+- Metrics: http://localhost:8081/metrics (Prometheus format with Go runtime stats)
+- Profiling: http://localhost:8081/debug/pprof/
+
+## Documentation
+
+### Protocol & Implementation
+- [Protocol Specification](docs/PROTOCOL.md) - Binary protocol definition
+- [Implementation Plan](docs/IMPLEMENTATION.md) - Development phases and progress
+- [Package Structure](docs/PACKAGES.md) - Code organization and package responsibilities
+- [Architecture Choices](docs/ARCHITECTURE.md) - Design decisions and patterns
+
+### Production Readiness
+- [Production Readiness Guide](docs/PRODUCTION_READINESS.md) - Requirements for production deployment
+
+## Algorithm Choice
+
+The server uses **SHA-256 based proof-of-work** with leading zero bits difficulty:
+- **Why SHA-256**: Cryptographically secure, well-tested, hardware-optimized
+- **Leading Zero Bits**: Simple difficulty scaling, easy verification
+- **HMAC Authentication**: Prevents challenge tampering and replay attacks
+- **Configurable Difficulty**: Adaptive to different threat levels (4-30 bits)
+
+This approach provides strong DDoS protection while remaining computationally reasonable for legitimate clients.
+
+## Current Status
+
+✅ **Complete**: Core functionality, TCP server, client, metrics, containerization  
+🔄 **In Progress**: Documentation (Phase 9)  
+📋 **Planned**: See [Production Readiness Guide](docs/PRODUCTION_READINESS.md) for production deployment requirements
+
+## Testing
+
+```bash
+# Run all tests
+go test ./...
+
+# Run integration tests
+go test ./test/integration/...
+
+# Benchmarks
+go test -bench=. ./internal/pow/...
+```
--- a/cmd/server/main.go
+++ b/cmd/server/main.go
@ -8,7 +8,6 @@ import (
 	"os"
 	"os/signal"
 	"syscall"
-	"time"

 	"hash-of-wisdom/internal/config"
 	"hash-of-wisdom/internal/lib/sl"
@ -64,6 +63,8 @@ func main() {
 		},
 	}

+	// Go runtime metrics are automatically registered by default registry
+
 	// Start metrics and pprof HTTP server
 	go func() {
 		http.Handle("/metrics", promhttp.Handler())
@ -73,31 +74,31 @@ func main() {
 		}
 	}()

+	// Create context that cancels on interrupt signals
+	ctx, cancel := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
+	defer cancel()
+
 	// Create server
 	srv := server.NewTCPServer(wisdomService, serverConfig,
 		server.WithLogger(logger))

 	// Start server
-	ctx := context.Background()
 	if err := srv.Start(ctx); err != nil {
 		logger.Error("failed to start server", sl.Err(err))
 		os.Exit(1)
 	}

-	// Wait for interrupt
-	sigChan := make(chan os.Signal, 1)
-	signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)
-
 	logger.Info("server ready - press ctrl+c to stop")
-	<-sigChan
+
+	// Wait for context cancellation (signal received)
+	<-ctx.Done()

 	// Graceful shutdown
 	logger.Info("shutting down server")
 	if err := srv.Stop(); err != nil {
 		logger.Error("error during shutdown", sl.Err(err))
+	} else {
+		logger.Info("server stopped gracefully")
 	}

-	// Give connections time to close
-	time.Sleep(100 * time.Millisecond)
-	logger.Info("server stopped")
 }
--- a/docs/ARCHITECTURE.md
+++ b/docs/ARCHITECTURE.md
@ -0,0 +1,330 @@
+# Architecture Choices
+
+This document explains the key architectural decisions made in the Hash of Wisdom project and the reasoning behind them.
+
+## Overall Architecture
+
+### Clean Architecture
+We follow Clean Architecture principles with clear layer separation:
+
+```
+┌─────────────────────────────────────┐
+│         Infrastructure Layer        │  ← cmd/, internal/server, internal/protocol
+├─────────────────────────────────────┤
+│         Application Layer           │  ← internal/application (message handling)
+├─────────────────────────────────────┤
+│           Domain Layer              │  ← internal/service, internal/pow (business logic)
+├─────────────────────────────────────┤
+│          External Layer             │  ← internal/quotes (external APIs)
+└─────────────────────────────────────┘
+```
+
+**Benefits**:
+- **Testability**: Each layer can be unit tested independently
+- **Maintainability**: Changes in one layer don't cascade
+- **Flexibility**: Easy to swap implementations (e.g., different quote sources)
+- **Domain Focus**: Core business rules are isolated and protected
+
+## Protocol Design
+
+### Binary Protocol with JSON Payloads
+Choice: Custom binary protocol with JSON-encoded message bodies
+
+**Why Binary Protocol**:
+- **Performance**: Efficient framing and length prefixes
+- **Reliability**: Clear message boundaries prevent parsing issues
+- **Extensibility**: Easy to add message types and versions
+
+**Why JSON Payloads**:
+- **Simplicity**: Standard library support, easy debugging
+- **Flexibility**: Schema evolution without breaking compatibility
+- **Tooling**: Excellent tooling and human readability
+
+**Alternative Considered**: Pure binary (Protocol Buffers)
+- **Rejected Because**: Added complexity without significant benefit for our use case
+- **Trade-off**: Slightly larger payload size for much simpler implementation
+
+### Stateless Challenge Design
+Choice: HMAC-signed challenges with all state embedded
+
+```go
+type Challenge struct {
+    Target     string `json:"target"`      // "quotes"
+    Timestamp  int64  `json:"timestamp"`   // Unix timestamp
+    Difficulty int    `json:"difficulty"`  // Leading zero bits
+    Random     string `json:"random"`      // Entropy
+    Signature  string `json:"signature"`   // HMAC-SHA256
+}
+```
+
+**Benefits**:
+- **Scalability**: No server-side session storage required
+- **Reliability**: Challenges survive server restarts
+- **Security**: HMAC prevents tampering and replay attacks
+- **Simplicity**: No cache management or cleanup needed
+
+**Alternative Considered**: Session-based challenges
+- **Rejected Because**: Requires distributed session management for horizontal scaling
+
+## Proof-of-Work Algorithm
+
+### SHA-256 with Leading Zero Bits
+Choice: SHA-256 hashing with difficulty measured as leading zero bits
+
+**Why SHA-256**:
+- **Security**: Cryptographically secure, extensively tested
+- **Performance**: Hardware-optimized on most platforms
+- **Standardization**: Well-known algorithm with predictable properties
+
+**Why Leading Zero Bits**:
+- **Linear Scaling**: Each bit doubles the difficulty (2^n complexity)
+- **Simplicity**: Easy to verify and understand
+- **Flexibility**: Fine-grained difficulty adjustment
+
+**Alternative Considered**: Scrypt/Argon2 (memory-hard functions)
+- **Rejected Because**: Excessive complexity for DDoS protection use case
+- **Trade-off**: ASIC resistance not needed for temporary challenges
+
+### Difficulty Range: 4-30 Bits
+Choice: Configurable difficulty with reasonable bounds
+
+- **Minimum (4 bits)**: ~16 attempts average, sub-second solve time
+- **Maximum (30 bits)**: ~1 billion attempts, several seconds on modern CPU
+- **Default (4 bits)**: Balance between protection and user experience
+
+## Server Architecture
+
+### TCP Server with Per-Connection Goroutines
+Choice: Custom TCP server with one goroutine per connection
+
+```go
+func (s *TCPServer) Start(ctx context.Context) error {
+    // Start listener
+    listener, err := net.Listen("tcp", s.config.Address)
+    if err != nil {
+        return err
+    }
+
+    // Start accept loop in goroutine
+    go s.acceptLoop(ctx)
+    return nil // Returns immediately
+}
+
+func (s *TCPServer) acceptLoop(ctx context.Context) {
+    for {
+        conn, err := s.listener.Accept()
+        if err != nil || ctx.Done() != nil {
+            return
+        }
+
+        // Launch handler in goroutine with WaitGroup tracking
+        s.wg.Add(1)
+        go func() {
+            defer s.wg.Done()
+            s.handleConnection(ctx, conn)
+        }()
+    }
+}
+```
+
+**Benefits**:
+- **Concurrency**: Each connection handled in separate goroutine
+- **Non-blocking Start**: Server starts in background, returns immediately
+- **Graceful Shutdown**: WaitGroup ensures all connections finish before stop
+- **Context Cancellation**: Proper cleanup when context is cancelled
+- **Resource Control**: Connection timeouts prevent resource exhaustion
+
+**Alternative Considered**: HTTP/REST API
+- **Rejected Because**: Test task requirements
+
+### Connection Security: Multi-Level Timeouts
+Choice: Layered timeout protection against various attacks
+
+1. **Connection Timeout (15s)**: Maximum total connection lifetime
+2. **Read Timeout (5s)**: Maximum time between incoming bytes
+3. **Write Timeout (5s)**: Maximum time to send response
+
+**Protects Against**:
+- **Slowloris**: Slow read timeout prevents slow header attacks
+- **Slow POST**: Connection timeout limits total request time
+- **Resource Exhaustion**: Automatic cleanup of stale connections
+
+## Configuration Management
+
+### cleanenv with YAML + Environment Variables
+Choice: File-based configuration with environment variable overrides
+
+```yaml
+# config.yaml
+server:
+  address: ":8080"
+
+pow:
+  difficulty: 4
+```
+
+```bash
+# Environment override
+export POW_DIFFICULTY=8
+```
+
+**Benefits**:
+- **Development**: Easy configuration files for local development
+- **Production**: Environment variables for containerized deployments
+- **Validation**: Built-in validation and type conversion
+- **Documentation**: Self-documenting with struct tags
+
+**Alternative Considered**: Pure environment variables
+- **Rejected Because**: Harder to manage complex configurations
+
+## Observability Architecture
+
+### Prometheus Metrics
+Choice: Prometheus format metrics with essential measurements
+
+**Application Metrics**:
+- `wisdom_requests_total` - All incoming requests
+- `wisdom_request_errors_total{error_type}` - Errors by type
+- `wisdom_request_duration_seconds` - Request processing time
+- `wisdom_quotes_served_total` - Successfully served quotes
+
+**Go Runtime Metrics** (automatically exported):
+- `go_memstats_*` - Memory allocation and GC statistics
+- `go_goroutines` - Current number of goroutines
+- `go_gc_duration_seconds` - Garbage collection duration
+- `process_*` - Process-level CPU, memory, and file descriptor stats
+
+**Design Principle**: Simple metrics that provide actionable insights
+- **Avoided**: Complex multi-dimensional metrics
+- **Focus**: Essential health and performance indicators
+- **Runtime Visibility**: Go collector provides deep runtime observability
+
+### Metrics at Infrastructure Layer
+Choice: Collect metrics in TCP server, not business logic
+
+```go
+// In TCP server (infrastructure)
+metrics.RequestsTotal.Inc()
+start := time.Now()
+response, err := s.wisdomApplication.HandleMessage(ctx, msg)
+metrics.RequestDuration.Observe(time.Since(start).Seconds())
+```
+
+**Benefits**:
+- **Separation of Concerns**: Business logic stays pure
+- **Consistency**: All requests measured the same way
+- **Performance**: Minimal overhead in critical path
+
+## Design Patterns
+
+### Dependency Injection
+All major components use constructor injection:
+```go
+server := server.NewTCPServer(wisdomApplication, config, options...)
+service := service.NewWisdomService(generator, verifier, quoteService)
+```
+
+**Benefits**:
+- **Testing**: Easy to inject mocks and stubs
+- **Configuration**: Runtime assembly of components
+- **Decoupling**: Components don't know about concrete implementations
+
+### Interface Segregation
+Small, focused interfaces for easy testing:
+```go
+type ChallengeGenerator interface {
+    GenerateChallenge(ctx context.Context) (*Challenge, error)
+}
+
+type QuoteService interface {
+    GetQuote(ctx context.Context) (string, error)
+}
+```
+
+### Functional Options
+Flexible configuration with sensible defaults:
+```go
+server := NewTCPServer(application, config,
+    WithLogger(logger),
+)
+```
+
+### Clean Architecture Implementation
+See the layer diagram in the Overall Architecture section above for package organization.
+
+## Testing Architecture
+
+### Layered Testing Strategy
+1. **Unit Tests**: Each package tested independently with mocks
+2. **Integration Tests**: End-to-end tests with real TCP connections
+3. **Benchmark Tests**: Performance validation for PoW algorithms
+
+```go
+// Unit test with mocks
+func TestWisdomService_HandleMessage(t *testing.T) {
+    mockGenerator := &MockGenerator{}
+    mockVerifier := &MockVerifier{}
+    mockQuotes := &MockQuoteService{}
+
+    service := NewWisdomService(mockGenerator, mockVerifier, mockQuotes)
+    // Test business logic in isolation
+}
+
+// Integration test with real components
+func TestTCPServer_SlowlorisProtection(t *testing.T) {
+    // Start real server, make slow connection
+    // Verify server doesn't hang
+}
+```
+
+## Security Architecture
+
+### Defense in Depth
+Multiple security layers working together:
+
+1. **HMAC Authentication**: Prevents challenge tampering
+2. **Timestamp Validation**: Prevents replay attacks (5-minute TTL)
+3. **Connection Timeouts**: Prevents resource exhaustion
+4. **Proof-of-Work**: Rate limiting through computational cost
+5. **Input Validation**: All protocol messages validated
+
+### Threat Model
+**Primary Threats Addressed**:
+- **DDoS Attacks**: PoW makes attacks expensive
+- **Resource Exhaustion**: Connection timeouts and limits
+- **Protocol Attacks**: Binary framing prevents confusion
+- **Replay Attacks**: Timestamp validation in challenges
+
+**Threats NOT Addressed** (by design):
+- **Authentication**: Public service, no user accounts
+- **Authorization**: All valid solutions get quotes
+- **Data Confidentiality**: Quotes are public information
+
+## Trade-offs Made
+
+### Simplicity vs Performance
+- **Chose**: Simple JSON payloads over binary serialization
+- **Trade-off**: ~30% larger messages for easier debugging and maintenance
+
+### Memory vs CPU
+- **Chose**: Stateless challenges requiring CPU verification
+- **Trade-off**: More CPU per request for better scalability
+
+### Flexibility vs Optimization
+- **Chose**: Interface-based design with dependency injection
+- **Trade-off**: Small runtime overhead for much better testability
+
+### Features vs Complexity
+- **Chose**: Essential features only (no rate limiting, user accounts, etc.)
+- **Benefit**: Clean, focused implementation that does one thing well
+
+## Future Architecture Considerations
+
+For production scaling, consider:
+1. **Quote Service Enhancement**: Caching, fallback quotes, multiple API sources
+2. **Load Balancing**: Multiple server instances behind load balancer
+3. **Rate Limiting**: Per-IP request limiting for additional protection
+4. **Monitoring**: Full observability stack (Prometheus, Grafana, alerting)
+5. **Security**: TLS encryption for sensitive deployments
+
+The current architecture provides a solid foundation for these enhancements while maintaining simplicity and focus.
--- a/docs/IMPLEMENTATION.md
+++ b/docs/IMPLEMENTATION.md
@ -109,6 +109,12 @@
 - [X] Implement configuration management using cleanenv library
 - [X] Read configuration from file with environment variable support

+## Phase 9: Documentation
+- [X] Create comprehensive README.md with project overview and quick start
+- [X] Document package structure and responsibilities
+- [X] Document architecture choices and design decisions
+- [X] Update production readiness assessment
+

 ## Directory Structure
 ```
--- a/docs/PACKAGES.md
+++ b/docs/PACKAGES.md
@ -0,0 +1,147 @@
+# Package Structure
+
+This document explains the organization and responsibilities of all packages in the Hash of Wisdom project.
+
+## Directory Structure
+
+```
+/
+├── cmd/                    # Application entry points
+│   ├── server/            # Server application
+│   └── client/            # Client application
+├── internal/              # Private application packages
+│   ├── application/      # Application layer (message handling)
+│   ├── config/           # Configuration management
+│   ├── lib/              # Shared utilities
+│   ├── metrics/          # Prometheus metrics
+│   ├── pow/              # Proof-of-Work implementation
+│   ├── protocol/         # Binary protocol codec
+│   ├── quotes/           # Quote service
+│   ├── server/           # TCP server implementation
+│   └── service/          # Business logic layer
+├── test/                 # Integration tests
+└── docs/                 # Documentation
+```
+
+## Package Responsibilities
+
+### `cmd/server`
+**Entry point for the TCP server application**
+- Parses command-line flags and configuration
+- Initializes all components with dependency injection
+- Starts TCP server and metrics endpoints
+- Handles graceful shutdown signals
+
+### `cmd/client`
+**Entry point for the client application**
+- Command-line interface for connecting to server
+- Handles proof-of-work solving on client side
+- Manages TCP connection lifecycle
+
+### `internal/config`
+**Configuration management with cleanenv**
+- Defines configuration structures with YAML/env tags
+- Loads configuration from files and environment variables
+- Provides sensible defaults for all settings
+- Supports both development and production configurations
+
+### `internal/lib/sl`
+**Shared logging utilities**
+- Structured logging helpers for consistent log formatting
+- Error attribute helpers for slog integration
+
+### `internal/metrics`
+**Prometheus metrics collection**
+- Defines application-specific metrics (requests, errors, duration)
+- Provides simple counters and histograms for monitoring
+- Integrated at the infrastructure layer (TCP server)
+
+### `internal/pow`
+**Proof-of-Work implementation**
+
+#### `internal/pow/challenge`
+- **Challenge Generation**: Creates HMAC-signed stateless challenges
+- **Verification**: Validates solutions against original challenges
+- **Security**: HMAC authentication prevents tampering
+- **Configuration**: Difficulty scaling, TTL management, secrets
+
+#### `internal/pow/solver`
+- **Solution Finding**: Brute-force nonce search with SHA-256
+- **Optimization**: Efficient bit counting for difficulty verification
+- **Client-side**: Used by client to solve server challenges
+
+### `internal/protocol`
+**Binary protocol codec**
+- **Message Types**: Challenge requests/responses, solution requests/responses, errors
+- **Encoding/Decoding**: JSON-based message serialization
+- **Streaming**: MessageDecoder for reading from TCP connections
+- **Validation**: Message structure and field validation
+- See [Protocol Specification](PROTOCOL.md) for detailed message flow and format
+
+### `internal/quotes`
+**Quote service implementation**
+- **HTTP Client**: Fetches quotes from external APIs using resty
+- **Interface**: Clean abstraction for quote retrieval
+- **Error Handling**: Graceful degradation for network issues
+- **Timeout Management**: Configurable request timeouts
+
+### `internal/server`
+**TCP server implementation**
+
+#### `internal/server/tcp.go`
+- **Connection Management**: Accept, handle, cleanup TCP connections
+- **Protocol Integration**: Uses protocol package for message handling
+- **Security**: Connection timeouts, slowloris protection
+- **Metrics**: Request tracking at infrastructure layer
+- **Lifecycle**: Graceful startup/shutdown with context
+
+#### `internal/server/config.go`
+- **Server Configuration**: Network settings, timeouts
+- **Functional Options**: Builder pattern for server customization
+
+### `internal/application`
+**Application layer (message handling and coordination)**
+- **WisdomApplication**: Protocol message handler and coordinator
+- **Message Processing**: Handles challenge and solution requests from protocol layer
+- **Response Generation**: Creates appropriate protocol responses
+- **Service Coordination**: Orchestrates calls to business logic layer
+- **Error Handling**: Converts service errors to protocol error responses
+
+### `internal/service`
+**Business logic layer (core domain services)**
+- **WisdomService**: Main business logic coordinator
+- **Challenge Workflow**: Manages challenge generation and validation
+- **Solution Workflow**: Handles solution verification and quote retrieval
+- **Clean Architecture**: Pure business logic, no I/O dependencies
+- **Testing**: Easily mockable interfaces for unit testing
+
+**Service Dependencies**:
+- `ChallengeGenerator` - Creates new challenges
+- `ChallengeVerifier` - Validates submitted solutions
+- `QuoteService` - Retrieves quotes after successful validation
+
+### `test/integration`
+**End-to-end integration tests**
+- **Slowloris Protection**: Tests server resilience against slow attacks
+- **Connection Timeouts**: Validates timeout configurations
+- **Full Workflow**: Tests complete client-server interaction
+- **Real Components**: Uses actual TCP connections and protocol
+
+## Dependency Flow
+
+```
+cmd/server
+    ↓
+internal/config → internal/server → internal/application → internal/service
+                      ↓                    ↓                   ↓
+                internal/protocol     internal/protocol   internal/pow
+                internal/metrics                         internal/quotes
+```
+
+## Architecture Benefits
+
+This package structure provides:
+- **Clear Separation**: Each package has a single, well-defined responsibility
+- **Testability**: Dependencies are injected, making testing straightforward
+- **Maintainability**: Changes are isolated to specific layers
+- **Scalability**: Clean interfaces allow for easy implementation swapping
--- a/docs/PRODUCTION_READINESS.md
+++ b/docs/PRODUCTION_READINESS.md
@ -0,0 +1,70 @@
+# Production Readiness Assessment
+
+## Current Implementation Status
+
+### ✅ Core Functionality (Complete)
+- **Proof of Work System**: SHA-256 hashcash with HMAC-signed stateless challenges
+- **Binary Protocol**: Custom TCP protocol with JSON payloads and proper framing
+- **TCP Server**: Connection handling with timeout protection against slowloris attacks
+- **Client Application**: CLI tool with challenge solving and solution submission
+- **Service Layer**: Clean architecture with dependency injection
+- **Quote System**: External API integration for inspirational quotes
+- **Security**: HMAC authentication, replay protection, input validation
+- **Testing**: Comprehensive unit tests and slowloris protection integration tests
+
+### ✅ Observability & Configuration (Complete)
+- **Metrics Endpoint**: Prometheus metrics at `/metrics` with application and Go runtime KPIs
+- **Application Metrics**: Request tracking, error categorization, duration histograms, quotes served
+- **Go Runtime Metrics**: Memory stats, GC metrics, goroutine counts, process stats (auto-registered)
+- **Profiler Endpoint**: Go pprof integration at `/debug/pprof/` for performance debugging
+- **Structured Logging**: slog integration throughout server components with consistent formatting
+- **Configuration**: cleanenv-based config management with YAML files and environment variables
+- **Containerization**: Production-ready Dockerfile with security best practices
+- **Error Handling**: Proper error propagation and categorization
+- **Graceful Shutdown**: Context-based shutdown with connection draining
+
+## Remaining Components for Production
+
+### Critical for Production
+1. **Connection Pooling & Resource Management** (worker pools, connection limits)
+2. **Rate Limiting & DDoS Protection**
+3. **Secret Management** (HMAC keys, external API credentials)
+4. **Advanced Monitoring & Alerting**
+5. **Advanced Configuration Management**
+6. **Health Checks** (graceful shutdown already implemented)
+
+### Important for Scale
+7. **Security Hardening**
+8. **Quote Service Enhancement** (caching, fallback quotes, multiple sources)
+9. **Load Testing & Performance**
+10. **Documentation & Runbooks**
+
+### Nice to Have
+11. **Advanced Observability**
+12. **Chaos Engineering**
+13. **Automated Deployment**
+
+## Risk Assessment
+
+### High Risk Areas
+- **No rate limiting**: Vulnerable to sophisticated DDoS attacks
+- **Hardcoded secrets**: HMAC keys in configuration files (not properly secured)
+- **Limited monitoring**: Basic metrics but no alerting or attack detection
+- **Single point of failure**: No redundancy or failover
+
+### Medium Risk Areas
+- **Memory management**: Potential leaks under high load
+- **External dependencies**: Quote API could become bottleneck
+- **Configuration drift**: Manual configuration prone to errors
+
+## Current Architecture Strengths
+
+The existing implementation provides an excellent foundation:
+- **Clean Architecture**: Proper separation of concerns with dependency injection
+- **Security-First Design**: HMAC authentication, replay protection, and timeout protection
+- **Stateless Operation**: HMAC-signed challenges enable horizontal scaling
+- **Graceful Shutdown**: Proper context handling and connection draining
+- **Comprehensive Testing**: Proven slowloris protection and unit test coverage
+- **Observability Ready**: Prometheus metrics, pprof profiling, structured logging
+- **Standard Protocols**: Industry-standard approaches (TCP, JSON, SHA-256)
+- **Container Ready**: Production Dockerfile with security best practices