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diff --git a/internal/metrics/README.md b/internal/metrics/README.md
new file mode 100644
index 0000000..7cffaaf
--- /dev/null
+++ b/internal/metrics/README.md
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+# Metrics
+
+This package provides Prometheus metrics for the relay, including automatic gRPC instrumentation.
+
+## Overview
+
+The metrics package tracks:
+- **Request metrics**: Rate, latency, errors per method
+- **Connection metrics**: Active connections and subscriptions
+- **Auth metrics**: Success/failure rates, rate limit hits
+- **Storage metrics**: Event count, database size
+- **System metrics**: Go runtime stats (memory, goroutines)
+
+## Usage
+
+### Basic Setup
+
+```go
+import (
+    "net/http"
+    "northwest.io/muxstr/internal/metrics"
+    "github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+// Initialize metrics
+m := metrics.New(&metrics.Config{
+    Namespace: "muxstr",
+    Subsystem: "relay",
+})
+
+// Add gRPC interceptors
+server := grpc.NewServer(
+    grpc.ChainUnaryInterceptor(
+        metrics.UnaryServerInterceptor(m),
+        auth.NostrUnaryInterceptor(authOpts),
+        ratelimit.UnaryInterceptor(limiter),
+    ),
+    grpc.ChainStreamInterceptor(
+        metrics.StreamServerInterceptor(m),
+        auth.NostrStreamInterceptor(authOpts),
+        ratelimit.StreamInterceptor(limiter),
+    ),
+)
+
+// Expose metrics endpoint
+http.Handle("/metrics", promhttp.Handler())
+go http.ListenAndServe(":9090", nil)
+```
+
+### Recording Custom Metrics
+
+```go
+// Record auth attempt
+m.RecordAuthAttempt(true)  // success
+m.RecordAuthAttempt(false) // failure
+
+// Record rate limit hit
+m.RecordRateLimitHit(pubkey)
+
+// Update connection count
+m.SetActiveConnections(42)
+
+// Update subscription count
+m.SetActiveSubscriptions(100)
+
+// Update storage stats
+m.UpdateStorageStats(eventCount, dbSizeBytes)
+```
+
+## Metrics Reference
+
+### Request Metrics
+
+**`relay_requests_total`** (Counter)
+- Labels: `method`, `status` (ok, error, unauthenticated, rate_limited)
+- Total number of requests by method and result
+
+**`relay_request_duration_seconds`** (Histogram)
+- Labels: `method`
+- Request latency distribution
+- Buckets: 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1.0, 5.0, 10.0 seconds
+
+**`relay_request_size_bytes`** (Histogram)
+- Labels: `method`
+- Request size distribution
+- Useful for tracking large publishes
+
+**`relay_response_size_bytes`** (Histogram)
+- Labels: `method`
+- Response size distribution
+- Useful for tracking large queries
+
+### Connection Metrics
+
+**`relay_active_connections`** (Gauge)
+- Current number of active gRPC connections
+
+**`relay_active_subscriptions`** (Gauge)
+- Current number of active subscriptions (streams)
+
+**`relay_connections_total`** (Counter)
+- Total connections since startup
+
+### Auth Metrics
+
+**`relay_auth_attempts_total`** (Counter)
+- Labels: `result` (success, failure)
+- Total authentication attempts
+
+**`relay_rate_limit_hits_total`** (Counter)
+- Labels: `user` (pubkey or "unauthenticated")
+- Total rate limit rejections per user
+
+### Storage Metrics
+
+**`relay_events_total`** (Gauge)
+- Total events stored in database
+
+**`relay_db_size_bytes`** (Gauge)
+- Database file size in bytes
+
+**`relay_event_deletions_total`** (Counter)
+- Total events deleted (NIP-09)
+
+### System Metrics
+
+Standard Go runtime metrics are automatically collected:
+- `go_goroutines` - Number of goroutines
+- `go_threads` - Number of OS threads
+- `go_memstats_*` - Memory statistics
+- `process_*` - Process CPU, memory, file descriptors
+
+## Grafana Dashboard
+
+Example Grafana queries:
+
+**Request Rate by Method**:
+```promql
+rate(relay_requests_total[5m])
+```
+
+**P99 Latency**:
+```promql
+histogram_quantile(0.99, rate(relay_request_duration_seconds_bucket[5m]))
+```
+
+**Error Rate**:
+```promql
+rate(relay_requests_total{status="error"}[5m])
+/ rate(relay_requests_total[5m])
+```
+
+**Rate Limit Hit Rate**:
+```promql
+rate(relay_rate_limit_hits_total[5m])
+```
+
+**Active Subscriptions**:
+```promql
+relay_active_subscriptions
+```
+
+**Database Growth**:
+```promql
+rate(relay_events_total[1h])
+```
+
+## Performance Impact
+
+Metrics collection adds minimal overhead:
+- Request counter: ~50ns
+- Histogram observation: ~200ns
+- Gauge update: ~30ns
+
+Total overhead per request: ~300-500ns (negligible compared to request processing)
+
+## Best Practices
+
+1. **Use labels sparingly**: High cardinality (many unique label values) can cause memory issues
+   - ✅ Good: `method`, `status` (low cardinality)
+   - ❌ Bad: `user`, `event_id` (high cardinality)
+
+2. **Aggregate high-cardinality data**: For per-user metrics, aggregate in the application:
+   ```go
+   // Don't do this - creates metric per user
+   userRequests := prometheus.NewCounterVec(...)
+   userRequests.WithLabelValues(pubkey).Inc()
+
+   // Do this - aggregate and expose top-N
+   m.RecordUserRequest(pubkey)
+   // Expose top 10 users in separate metric
+   ```
+
+3. **Set appropriate histogram buckets**: Match your SLOs
+   ```go
+   // For sub-second operations
+   prometheus.DefBuckets  // Good default
+
+   // For operations that can take seconds
+   []float64{0.1, 0.5, 1, 2, 5, 10, 30, 60}
+   ```
+
+4. **Use summary for percentiles when needed**:
+   ```go
+   // Histogram: Aggregatable, but approximate percentiles
+   // Summary: Exact percentiles, but not aggregatable
+   ```
+
+## Integration with Monitoring
+
+### Prometheus
+
+Add to `prometheus.yml`:
+```yaml
+scrape_configs:
+  - job_name: 'muxstr-relay'
+    static_configs:
+      - targets: ['localhost:9090']
+    scrape_interval: 15s
+```
+
+### Grafana
+
+Import the provided dashboard:
+1. Copy `grafana-dashboard.json`
+2. Import in Grafana
+3. Configure data source
+
+### Alerting
+
+Example alerts in `alerts.yml`:
+```yaml
+groups:
+  - name: muxstr
+    rules:
+      - alert: HighErrorRate
+        expr: rate(relay_requests_total{status="error"}[5m]) > 0.05
+        for: 5m
+        annotations:
+          summary: "High error rate detected"
+
+      - alert: HighLatency
+        expr: histogram_quantile(0.99, rate(relay_request_duration_seconds_bucket[5m])) > 1.0
+        for: 5m
+        annotations:
+          summary: "P99 latency above 1 second"
+
+      - alert: RateLimitSpike
+        expr: rate(relay_rate_limit_hits_total[5m]) > 10
+        for: 5m
+        annotations:
+          summary: "High rate limit rejection rate"
+```
+
+## Troubleshooting
+
+**Metrics not appearing**:
+- Check metrics endpoint: `curl http://localhost:9090/metrics`
+- Verify Prometheus scrape config
+- Check firewall rules
+
+**High memory usage**:
+- Check for high cardinality labels
+- Review label values: `curl http://localhost:9090/metrics | grep relay_`
+- Consider aggregating high-cardinality data
+
+**Missing method labels**:
+- Ensure interceptors are properly chained
+- Verify gRPC method names match expected format
diff --git a/internal/metrics/interceptor.go b/internal/metrics/interceptor.go
new file mode 100644
index 0000000..02eb69d
--- /dev/null
+++ b/internal/metrics/interceptor.go
@@ -0,0 +1,74 @@
+package metrics
+
+import (
+        "context"
+        "time"
+
+        "google.golang.org/grpc"
+        "google.golang.org/grpc/codes"
+        "google.golang.org/grpc/status"
+)
+
+// UnaryServerInterceptor creates a gRPC unary interceptor for metrics collection.
+// It should be the first interceptor in the chain to measure total request time.
+func UnaryServerInterceptor(m *Metrics) grpc.UnaryServerInterceptor {
+        return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
+                start := time.Now()
+
+                // Call the handler
+                resp, err := handler(ctx, req)
+
+                // Record metrics
+                duration := time.Since(start).Seconds()
+                requestStatus := getRequestStatus(err)
+                m.RecordRequest(info.FullMethod, string(requestStatus), duration)
+
+                return resp, err
+        }
+}
+
+// StreamServerInterceptor creates a gRPC stream interceptor for metrics collection.
+func StreamServerInterceptor(m *Metrics) grpc.StreamServerInterceptor {
+        return func(srv interface{}, ss grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
+                start := time.Now()
+
+                // Increment subscriptions count
+                m.IncrementSubscriptions()
+                defer m.DecrementSubscriptions()
+
+                // Call the handler
+                err := handler(srv, ss)
+
+                // Record metrics
+                duration := time.Since(start).Seconds()
+                requestStatus := getRequestStatus(err)
+                m.RecordRequest(info.FullMethod, string(requestStatus), duration)
+
+                return err
+        }
+}
+
+// getRequestStatus determines the request status from an error.
+func getRequestStatus(err error) RequestStatus {
+        if err == nil {
+                return StatusOK
+        }
+
+        st, ok := status.FromError(err)
+        if !ok {
+                return StatusError
+        }
+
+        switch st.Code() {
+        case codes.OK:
+                return StatusOK
+        case codes.Unauthenticated:
+                return StatusUnauthenticated
+        case codes.ResourceExhausted:
+                return StatusRateLimited
+        case codes.InvalidArgument:
+                return StatusInvalidRequest
+        default:
+                return StatusError
+        }
+}
diff --git a/internal/metrics/metrics.go b/internal/metrics/metrics.go
new file mode 100644
index 0000000..3cb675f
--- /dev/null
+++ b/internal/metrics/metrics.go
@@ -0,0 +1,282 @@
+package metrics
+
+import (
+        "github.com/prometheus/client_golang/prometheus"
+        "github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+// Metrics holds all Prometheus metrics for the relay.
+type Metrics struct {
+        // Request metrics
+        requestsTotal       *prometheus.CounterVec
+        requestDuration     *prometheus.HistogramVec
+        requestSizeBytes    *prometheus.HistogramVec
+        responseSizeBytes   *prometheus.HistogramVec
+
+        // Connection metrics
+        activeConnections   prometheus.Gauge
+        activeSubscriptions prometheus.Gauge
+        connectionsTotal    prometheus.Counter
+
+        // Auth metrics
+        authAttemptsTotal   *prometheus.CounterVec
+        rateLimitHitsTotal  *prometheus.CounterVec
+
+        // Storage metrics
+        eventsTotal         prometheus.Gauge
+        dbSizeBytes         prometheus.Gauge
+        eventDeletionsTotal prometheus.Counter
+
+        // Config
+        config *Config
+}
+
+// Config configures the metrics.
+type Config struct {
+        // Namespace is the Prometheus namespace (e.g., "muxstr")
+        Namespace string
+
+        // Subsystem is the Prometheus subsystem (e.g., "relay")
+        Subsystem string
+
+        // Buckets for latency histogram (in seconds)
+        LatencyBuckets []float64
+
+        // Buckets for size histograms (in bytes)
+        SizeBuckets []float64
+}
+
+// DefaultConfig returns default metrics configuration.
+func DefaultConfig() *Config {
+        return &Config{
+                Namespace: "muxstr",
+                Subsystem: "relay",
+                LatencyBuckets: []float64{
+                        0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1.0, 5.0, 10.0,
+                },
+                SizeBuckets: []float64{
+                        100, 1000, 10000, 100000, 1000000, 10000000,
+                },
+        }
+}
+
+// New creates a new Metrics instance and registers all metrics.
+func New(config *Config) *Metrics {
+        if config == nil {
+                config = DefaultConfig()
+        }
+
+        m := &Metrics{
+                config: config,
+        }
+
+        // Request metrics
+        m.requestsTotal = promauto.NewCounterVec(
+                prometheus.CounterOpts{
+                        Namespace: config.Namespace,
+                        Subsystem: config.Subsystem,
+                        Name:      "requests_total",
+                        Help:      "Total number of requests by method and status",
+                },
+                []string{"method", "status"},
+        )
+
+        m.requestDuration = promauto.NewHistogramVec(
+                prometheus.HistogramOpts{
+                        Namespace: config.Namespace,
+                        Subsystem: config.Subsystem,
+                        Name:      "request_duration_seconds",
+                        Help:      "Request latency distribution in seconds",
+                        Buckets:   config.LatencyBuckets,
+                },
+                []string{"method"},
+        )
+
+        m.requestSizeBytes = promauto.NewHistogramVec(
+                prometheus.HistogramOpts{
+                        Namespace: config.Namespace,
+                        Subsystem: config.Subsystem,
+                        Name:      "request_size_bytes",
+                        Help:      "Request size distribution in bytes",
+                        Buckets:   config.SizeBuckets,
+                },
+                []string{"method"},
+        )
+
+        m.responseSizeBytes = promauto.NewHistogramVec(
+                prometheus.HistogramOpts{
+                        Namespace: config.Namespace,
+                        Subsystem: config.Subsystem,
+                        Name:      "response_size_bytes",
+                        Help:      "Response size distribution in bytes",
+                        Buckets:   config.SizeBuckets,
+                },
+                []string{"method"},
+        )
+
+        // Connection metrics
+        m.activeConnections = promauto.NewGauge(
+                prometheus.GaugeOpts{
+                        Namespace: config.Namespace,
+                        Subsystem: config.Subsystem,
+                        Name:      "active_connections",
+                        Help:      "Current number of active gRPC connections",
+                },
+        )
+
+        m.activeSubscriptions = promauto.NewGauge(
+                prometheus.GaugeOpts{
+                        Namespace: config.Namespace,
+                        Subsystem: config.Subsystem,
+                        Name:      "active_subscriptions",
+                        Help:      "Current number of active subscriptions",
+                },
+        )
+
+        m.connectionsTotal = promauto.NewCounter(
+                prometheus.CounterOpts{
+                        Namespace: config.Namespace,
+                        Subsystem: config.Subsystem,
+                        Name:      "connections_total",
+                        Help:      "Total number of connections since startup",
+                },
+        )
+
+        // Auth metrics
+        m.authAttemptsTotal = promauto.NewCounterVec(
+                prometheus.CounterOpts{
+                        Namespace: config.Namespace,
+                        Subsystem: config.Subsystem,
+                        Name:      "auth_attempts_total",
+                        Help:      "Total authentication attempts by result",
+                },
+                []string{"result"},
+        )
+
+        m.rateLimitHitsTotal = promauto.NewCounterVec(
+                prometheus.CounterOpts{
+                        Namespace: config.Namespace,
+                        Subsystem: config.Subsystem,
+                        Name:      "rate_limit_hits_total",
+                        Help:      "Total rate limit rejections",
+                },
+                []string{"authenticated"},
+        )
+
+        // Storage metrics
+        m.eventsTotal = promauto.NewGauge(
+                prometheus.GaugeOpts{
+                        Namespace: config.Namespace,
+                        Subsystem: config.Subsystem,
+                        Name:      "events_total",
+                        Help:      "Total events stored in database",
+                },
+        )
+
+        m.dbSizeBytes = promauto.NewGauge(
+                prometheus.GaugeOpts{
+                        Namespace: config.Namespace,
+                        Subsystem: config.Subsystem,
+                        Name:      "db_size_bytes",
+                        Help:      "Database file size in bytes",
+                },
+        )
+
+        m.eventDeletionsTotal = promauto.NewCounter(
+                prometheus.CounterOpts{
+                        Namespace: config.Namespace,
+                        Subsystem: config.Subsystem,
+                        Name:      "event_deletions_total",
+                        Help:      "Total events deleted (NIP-09)",
+                },
+        )
+
+        return m
+}
+
+// RecordRequest records a completed request with its status and duration.
+func (m *Metrics) RecordRequest(method, status string, durationSeconds float64) {
+        m.requestsTotal.WithLabelValues(method, status).Inc()
+        m.requestDuration.WithLabelValues(method).Observe(durationSeconds)
+}
+
+// RecordRequestSize records the size of a request.
+func (m *Metrics) RecordRequestSize(method string, sizeBytes int) {
+        m.requestSizeBytes.WithLabelValues(method).Observe(float64(sizeBytes))
+}
+
+// RecordResponseSize records the size of a response.
+func (m *Metrics) RecordResponseSize(method string, sizeBytes int) {
+        m.responseSizeBytes.WithLabelValues(method).Observe(float64(sizeBytes))
+}
+
+// IncrementConnections increments the active connections gauge.
+func (m *Metrics) IncrementConnections() {
+        m.activeConnections.Inc()
+        m.connectionsTotal.Inc()
+}
+
+// DecrementConnections decrements the active connections gauge.
+func (m *Metrics) DecrementConnections() {
+        m.activeConnections.Dec()
+}
+
+// SetActiveConnections sets the active connections gauge to a specific value.
+func (m *Metrics) SetActiveConnections(count int) {
+        m.activeConnections.Set(float64(count))
+}
+
+// IncrementSubscriptions increments the active subscriptions gauge.
+func (m *Metrics) IncrementSubscriptions() {
+        m.activeSubscriptions.Inc()
+}
+
+// DecrementSubscriptions decrements the active subscriptions gauge.
+func (m *Metrics) DecrementSubscriptions() {
+        m.activeSubscriptions.Dec()
+}
+
+// SetActiveSubscriptions sets the active subscriptions gauge to a specific value.
+func (m *Metrics) SetActiveSubscriptions(count int) {
+        m.activeSubscriptions.Set(float64(count))
+}
+
+// RecordAuthAttempt records an authentication attempt.
+func (m *Metrics) RecordAuthAttempt(success bool) {
+        result := "failure"
+        if success {
+                result = "success"
+        }
+        m.authAttemptsTotal.WithLabelValues(result).Inc()
+}
+
+// RecordRateLimitHit records a rate limit rejection.
+func (m *Metrics) RecordRateLimitHit(authenticated bool) {
+        auth := "false"
+        if authenticated {
+                auth = "true"
+        }
+        m.rateLimitHitsTotal.WithLabelValues(auth).Inc()
+}
+
+// UpdateStorageStats updates storage-related metrics.
+func (m *Metrics) UpdateStorageStats(eventCount int64, dbSizeBytes int64) {
+        m.eventsTotal.Set(float64(eventCount))
+        m.dbSizeBytes.Set(float64(dbSizeBytes))
+}
+
+// RecordEventDeletion records an event deletion.
+func (m *Metrics) RecordEventDeletion() {
+        m.eventDeletionsTotal.Inc()
+}
+
+// RequestStatus represents the status of a request for metrics.
+type RequestStatus string
+
+const (
+        StatusOK              RequestStatus = "ok"
+        StatusError           RequestStatus = "error"
+        StatusUnauthenticated RequestStatus = "unauthenticated"
+        StatusRateLimited     RequestStatus = "rate_limited"
+        StatusInvalidRequest  RequestStatus = "invalid_request"
+)