feat(kv-router): add Prometheus metrics to standalone indexer (#7339)

Signed-off-by: PeaBrane <yanrpei@gmail.com>

feat(kv-router): add Prometheus metrics to standalone indexer (#7339)
Signed-off-by: PeaBrane <yanrpei@gmail.com>
5aa2f53f · Yan Ru Pei · GitHub · c8f7ce90 · 5aa2f53f · 5aa2f53f
Unverified Commit 5aa2f53f authored Mar 13, 2026 by Yan Ru Pei Committed by GitHub Mar 13, 2026
9 changed files
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -72,9 +72,9 @@ checksum = "4b46cbb362ab8752921c97e041f5e366ee6297bd428a31275b9fcf1e380f7299"

 [[package]]
 name = "anstream"
-version = "0.6.21"
+version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "43d5b281e737544384e969a5ccad3f1cdd24b48086a0fc1b2a5262a26b8f4f4a"
+checksum = "824a212faf96e9acacdbd09febd34438f8f711fb84e09a8916013cd7815ca28d"
 dependencies = [
 "anstyle",
 "anstyle-parse",
@@ -93,9 +93,9 @@ checksum = "5192cca8006f1fd4f7237516f40fa183bb07f8fbdfedaa0036de5ea9b0b45e78"

 [[package]]
 name = "anstyle-parse"
-version = "0.2.7"
+version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4e7644824f0aa2c7b9384579234ef10eb7efb6a0deb83f9630a49594dd9c15c2"
+checksum = "52ce7f38b242319f7cabaa6813055467063ecdc9d355bbb4ce0c68908cd8130e"
 dependencies = [
 "utf8parse",
 ]
@@ -871,7 +871,7 @@ version = "0.27.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3fce8dd7fcfcbf3a0a87d8f515194b49d6135acab73e18bd380d1d93bb1a15eb"
 dependencies = [
- "clap 4.5.60",
+ "clap 4.6.0",
 "heck 0.4.1",
 "indexmap 2.13.0",
 "log",
@@ -998,9 +998,9 @@ dependencies = [

 [[package]]
 name = "clap"
-version = "4.5.60"
+version = "4.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2797f34da339ce31042b27d23607e051786132987f595b02ba4f6a6dffb7030a"
+checksum = "b193af5b67834b676abd72466a96c1024e6a6ad978a1f484bd90b85c94041351"
 dependencies = [
 "clap_builder",
 "clap_derive",
@@ -1008,9 +1008,9 @@ dependencies = [

 [[package]]
 name = "clap_builder"
-version = "4.5.60"
+version = "4.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "24a241312cea5059b13574bb9b3861cabf758b879c15190b37b6d6fd63ab6876"
+checksum = "714a53001bf66416adb0e2ef5ac857140e7dc3a0c48fb28b2f10762fc4b5069f"
 dependencies = [
 "anstream",
 "anstyle",
@@ -1020,9 +1020,9 @@ dependencies = [

 [[package]]
 name = "clap_derive"
-version = "4.5.55"
+version = "4.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a92793da1a46a5f2a02a6f4c46c6496b28c43638adea8306fcb0caa1634f24e5"
+checksum = "1110bd8a634a1ab8cb04345d8d878267d57c3cf1b38d91b71af6686408bbca6a"
 dependencies = [
 "heck 0.5.0",
 "proc-macro2",
@@ -1032,9 +1032,9 @@ dependencies = [

 [[package]]
 name = "clap_lex"
-version = "1.0.0"
+version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3a822ea5bc7590f9d40f1ba12c0dc3c2760f3482c6984db1573ad11031420831"
+checksum = "c8d4a3bb8b1e0c1050499d1815f5ab16d04f0959b233085fb31653fbfc9d98f9"

 [[package]]
 name = "cmake"
@@ -1092,9 +1092,9 @@ dependencies = [

 [[package]]
 name = "config"
-version = "0.15.19"
+version = "0.15.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b30fa8254caad766fc03cb0ccae691e14bf3bd72bfff27f72802ce729551b3d6"
+checksum = "4fe5feec195269515c4722937cd7ffcfe7b4205d18d2e6577b7223ecb159ab00"
 dependencies = [
 "async-trait",
 "convert_case",
@@ -1105,7 +1105,7 @@ dependencies = [
 "serde-untagged",
 "serde_core",
 "serde_json",
- "toml 0.9.12+spec-1.1.0",
+ "toml 1.0.6+spec-1.1.0",
 "winnow",
 "yaml-rust2",
 ]
@@ -1304,7 +1304,7 @@ dependencies = [
 "anes",
 "cast",
 "ciborium",
- "clap 4.5.60",
+ "clap 4.6.0",
 "criterion-plot 0.5.0",
 "futures",
 "is-terminal",
@@ -1847,7 +1847,7 @@ version = "1.0.0"
 dependencies = [
 "anyhow",
 "async-trait",
- "clap 4.5.60",
+ "clap 4.6.0",
 "dynamo-kv-router",
 "dynamo-mocker",
 "dynamo-tokens",
@@ -1888,7 +1888,7 @@ dependencies = [
 "async-trait",
 "axum 0.8.4",
 "bytes",
- "clap 4.5.60",
+ "clap 4.6.0",
 "dashmap 6.1.0",
 "derive-getters",
 "derive_builder",
@@ -1941,7 +1941,7 @@ dependencies = [
 "bytemuck",
 "bytes",
 "chrono",
- "clap 4.5.60",
+ "clap 4.6.0",
 "criterion 0.3.6",
 "cudarc",
 "dashmap 5.5.3",
@@ -3709,7 +3709,7 @@ dependencies = [
 "anyhow",
 "base64 0.21.7",
 "bytecount",
- "clap 4.5.60",
+ "clap 4.6.0",
 "fancy-regex 0.11.0",
 "fraction",
 "getrandom 0.2.17",
@@ -3902,7 +3902,7 @@ dependencies = [
 name = "kvbm-kernels"
 version = "0.1.0"
 dependencies = [
- "clap 4.5.60",
+ "clap 4.6.0",
 "cudarc",
 "half 2.7.1",
 "ndarray 0.17.2",
@@ -4446,7 +4446,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a9929c605e135347ccda5e0e7ff0627217f23189915a5c3971265ce490a14abf"
 dependencies = [
 "anyhow",
- "clap 4.5.60",
+ "clap 4.6.0",
 "colored",
 "futures",
 "modelexpress-common",
@@ -4470,7 +4470,7 @@ dependencies = [
 "anyhow",
 "async-trait",
 "chrono",
- "clap 4.5.60",
+ "clap 4.6.0",
 "config",
 "hf-hub",
 "jiff",
@@ -5080,9 +5080,9 @@ dependencies = [

 [[package]]
 name = "once_cell"
-version = "1.21.3"
+version = "1.21.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "42f5e15c9953c5e4ccceeb2e7382a716482c34515315f7b03532b8b4e8393d2d"
+checksum = "9f7c3e4beb33f85d45ae3e3a1792185706c8e16d043238c593331cc7cd313b50"

 [[package]]
 name = "once_cell_polyfill"
@@ -5133,7 +5133,7 @@ dependencies = [
 "anyhow",
 "base64 0.22.1",
 "bstr",
- "clap 4.5.60",
+ "clap 4.6.0",
 "fancy-regex 0.13.0",
 "futures",
 "image",
@@ -7893,13 +7893,13 @@ dependencies = [

 [[package]]
 name = "toml"
-version = "0.9.12+spec-1.1.0"
+version = "1.0.6+spec-1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cf92845e79fc2e2def6a5d828f0801e29a2f8acc037becc5ab08595c7d5e9863"
+checksum = "399b1124a3c9e16766831c6bba21e50192572cdd98706ea114f9502509686ffc"
 dependencies = [
 "serde_core",
 "serde_spanned 1.0.4",
- "toml_datetime 0.7.5+spec-1.1.0",
+ "toml_datetime 1.0.0+spec-1.1.0",
 "toml_parser",
 "winnow",
 ]
@@ -7913,15 +7913,6 @@ dependencies = [
 "serde",
 ]

-[[package]]
-name = "toml_datetime"
-version = "0.7.5+spec-1.1.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "92e1cfed4a3038bc5a127e35a2d360f145e1f4b971b551a2ba5fd7aedf7e1347"
-dependencies = [
- "serde_core",
-]
-
 [[package]]
 name = "toml_datetime"
 version = "1.0.0+spec-1.1.0"
@@ -9687,9 +9678,9 @@ dependencies = [

 [[package]]
 name = "zune-jpeg"
-version = "0.5.12"
+version = "0.5.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "410e9ecef634c709e3831c2cfdb8d9c32164fae1c67496d5b68fff728eec37fe"
+checksum = "ec5f41c76397b7da451efd19915684f727d7e1d516384ca6bd0ec43ec94de23c"
 dependencies = [
 "zune-core",
 ]
--- a/docs/components/router/standalone-indexer.md
+++ b/docs/components/router/standalone-indexer.md
@@ -99,6 +99,30 @@ dynamo-kv-indexer --port 8090 [--threads 4] [--block-size 16 --model-name my-mod

 ## HTTP API

+### `GET /health` — Liveness check
+
+Returns `200 OK` unconditionally.
+
+```bash
+curl http://localhost:8090/health
+```
+
+### `GET /metrics` — Prometheus metrics
+
+Returns metrics in Prometheus text exposition format. Available when the binary is built with the `metrics` feature (enabled by default via `standalone-indexer`).
+
+```bash
+curl http://localhost:8090/metrics
+```
+
+| Metric | Type | Labels | Description |
+|--------|------|--------|-------------|
+| `dynamo_kvindexer_request_duration_seconds` | Histogram | `endpoint` | HTTP request latency |
+| `dynamo_kvindexer_requests_total` | Counter | `endpoint`, `method` | Total HTTP requests |
+| `dynamo_kvindexer_errors_total` | Counter | `endpoint`, `status_class` | HTTP error responses (4xx/5xx) |
+| `dynamo_kvindexer_models` | Gauge | — | Number of active model+tenant indexers |
+| `dynamo_kvindexer_workers` | Gauge | — | Number of registered worker instances |
+
 ### `POST /register` — Register an endpoint

 Register a ZMQ endpoint for an instance. Each call creates or reuses the indexer for the given `(model_name, tenant_id)` pair.
@@ -307,7 +331,7 @@ graph TD
        REG[Worker Registry]
        ZMQ[ZMQ SUB Listeners]
        IDX["Indexer Map<br/>(model, tenant) → Radix Tree"]
-        HTTP[HTTP API<br/>/query /dump /register]
+        HTTP[HTTP API<br/>/query /dump /register /metrics /health]
    end

    CLIENT[External Client]

--- a/lib/bindings/python/src/dynamo/prometheus_names.py
+++ b/lib/bindings/python/src/dynamo/prometheus_names.py
@@ -132,6 +132,13 @@ class frontend_service:
    OPERATION_LABEL = "operation"


+class kv_publisher:
+    """KV Publisher metrics"""
+
+    # Total number of raw events dropped by engines before reaching publisher (detected via event_id gaps)
+    ENGINES_DROPPED_EVENTS_TOTAL = "kv_publisher_engines_dropped_events_total"
+
+
 class kvbm:
    """KVBM"""

@@ -167,6 +174,21 @@ class kvbm:
    OBJECT_WRITE_FAILURES = "object_write_failures"


+class kvindexer:
+    """Standalone KV indexer HTTP service metrics"""
+
+    # HTTP request latency
+    REQUEST_DURATION_SECONDS = "request_duration_seconds"
+    # Total HTTP requests
+    REQUESTS_TOTAL = "requests_total"
+    # HTTP error responses (4xx/5xx)
+    ERRORS_TOTAL = "errors_total"
+    # Number of active model+tenant indexers
+    MODELS = "models"
+    # Number of registered worker instances
+    WORKERS = "workers"
+
+
 class kvrouter:
    # Number of KV cache events applied to the index (including status)
    KV_CACHE_EVENTS_APPLIED = "kv_cache_events_applied"
@@ -225,6 +247,8 @@ class name_prefix:
    ROUTER = "dynamo_router"
    # Prefix for tokio runtime metrics
    TOKIO = "dynamo_tokio"
+    # Prefix for standalone KV indexer metrics
+    KVINDEXER = "dynamo_kvindexer"


 class router:
@@ -265,25 +289,6 @@ class routing_overhead:
    TOTAL_MS = "overhead_total_ms"


-class trtllm_additional:
-    """Additional TRT-LLM worker metrics beyond what the engine natively provides."""
-
-    # Total number of aborted/cancelled requests
-    NUM_ABORTED_REQUESTS_TOTAL = "trtllm_num_aborted_requests_total"
-    # Total number of requests containing image content
-    REQUEST_TYPE_IMAGE_TOTAL = "trtllm_request_type_image_total"
-    # Total number of requests using guided/structured decoding
-    REQUEST_TYPE_STRUCTURED_OUTPUT_TOTAL = "trtllm_request_type_structured_output_total"
-    # Total number of successful KV cache transfers
-    KV_TRANSFER_SUCCESS_TOTAL = "trtllm_kv_transfer_success_total"
-    # KV cache transfer latency per request in seconds
-    KV_TRANSFER_LATENCY_SECONDS = "trtllm_kv_transfer_latency_seconds"
-    # KV cache transfer size per request in bytes
-    KV_TRANSFER_BYTES = "trtllm_kv_transfer_bytes"
-    # KV cache transfer speed per request in GB/s
-    KV_TRANSFER_SPEED_GB_S = "trtllm_kv_transfer_speed_gb_s"
-
-
 class task_tracker:
    """Task tracker Prometheus metric name suffixes"""

@@ -318,6 +323,25 @@ class tokio_perf:
    ALIVE_TASKS = "alive_tasks"


+class trtllm_additional:
+    """Additional TRT-LLM worker metrics beyond what the engine natively provides."""
+
+    # Total number of aborted/cancelled requests
+    NUM_ABORTED_REQUESTS_TOTAL = "trtllm_num_aborted_requests_total"
+    # Total number of requests containing image content
+    REQUEST_TYPE_IMAGE_TOTAL = "trtllm_request_type_image_total"
+    # Total number of requests using guided/structured decoding
+    REQUEST_TYPE_STRUCTURED_OUTPUT_TOTAL = "trtllm_request_type_structured_output_total"
+    # Total number of successful KV cache transfers
+    KV_TRANSFER_SUCCESS_TOTAL = "trtllm_kv_transfer_success_total"
+    # KV cache transfer latency per request in seconds
+    KV_TRANSFER_LATENCY_SECONDS = "trtllm_kv_transfer_latency_seconds"
+    # KV cache transfer size per request in bytes
+    KV_TRANSFER_BYTES = "trtllm_kv_transfer_bytes"
+    # KV cache transfer speed per request in GB/s
+    KV_TRANSFER_SPEED_GB_S = "trtllm_kv_transfer_speed_gb_s"
+
+
 class work_handler:
    """Work handler Prometheus metric names"""


--- a/lib/kv-router/Cargo.toml
+++ b/lib/kv-router/Cargo.toml
@@ -12,7 +12,7 @@ repository.workspace = true

 [features]
 default = []
-metrics = []
+metrics = ["dep:dynamo-runtime"]
 bench = ["dep:clap", "dep:indicatif", "dep:serde_json", "dep:plotters"]
 standalone-indexer = ["metrics", "dep:axum", "dep:bytes", "dep:zeromq", "dep:serde_json", "dep:reqwest"]
 indexer-bin = ["standalone-indexer", "dep:clap", "dep:tracing-subscriber"]
@@ -20,7 +20,7 @@ test-endpoints = ["indexer-bin"]

 [dependencies]
 # repo
-dynamo-runtime = { workspace = true }
+dynamo-runtime = { workspace = true, optional = true }
 dynamo-tokens = { workspace = true }

 # workspace

--- a/lib/kv-router/src/standalone_indexer/metrics.rs
+++ b/lib/kv-router/src/standalone_indexer/metrics.rs
+// SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+#[cfg(feature = "metrics")]
+use std::sync::LazyLock;
+#[cfg(feature = "metrics")]
+use std::time::Instant;
+
+#[cfg(feature = "metrics")]
+use axum::{extract::MatchedPath, http::Request, middleware::Next, response::Response};
+#[cfg(feature = "metrics")]
+use dynamo_runtime::metrics::prometheus_names::{kvindexer, name_prefix};
+#[cfg(feature = "metrics")]
+use prometheus::{
+    HistogramVec, IntCounterVec, IntGauge, Opts, exponential_buckets, histogram_opts,
+};
+
+#[cfg(feature = "metrics")]
+pub struct StandaloneIndexerMetrics {
+    pub request_duration: HistogramVec,
+    pub requests_total: IntCounterVec,
+    pub errors_total: IntCounterVec,
+    pub models: IntGauge,
+    pub workers: IntGauge,
+}
+
+#[cfg(feature = "metrics")]
+static METRICS: LazyLock<StandaloneIndexerMetrics> = LazyLock::new(|| {
+    let prefix = name_prefix::KVINDEXER;
+    StandaloneIndexerMetrics {
+        request_duration: HistogramVec::new(
+            histogram_opts!(
+                format!("{prefix}_{}", kvindexer::REQUEST_DURATION_SECONDS),
+                "HTTP request latency",
+                exponential_buckets(0.0001, 2.0, 20).expect("valid bucket params")
+            ),
+            &["endpoint"],
+        )
+        .expect("valid histogram"),
+        requests_total: IntCounterVec::new(
+            Opts::new(
+                format!("{prefix}_{}", kvindexer::REQUESTS_TOTAL),
+                "Total HTTP requests",
+            ),
+            &["endpoint", "method"],
+        )
+        .expect("valid counter"),
+        errors_total: IntCounterVec::new(
+            Opts::new(
+                format!("{prefix}_{}", kvindexer::ERRORS_TOTAL),
+                "HTTP error responses (4xx/5xx)",
+            ),
+            &["endpoint", "status_class"],
+        )
+        .expect("valid counter"),
+        models: IntGauge::new(
+            format!("{prefix}_{}", kvindexer::MODELS),
+            "Number of active model+tenant indexers",
+        )
+        .expect("valid gauge"),
+        workers: IntGauge::new(
+            format!("{prefix}_{}", kvindexer::WORKERS),
+            "Number of registered worker instances",
+        )
+        .expect("valid gauge"),
+    }
+});
+
+#[cfg(feature = "metrics")]
+pub fn register(registry: &prometheus::Registry) -> Result<(), prometheus::Error> {
+    let m = &*METRICS;
+    registry.register(Box::new(m.request_duration.clone()))?;
+    registry.register(Box::new(m.requests_total.clone()))?;
+    registry.register(Box::new(m.errors_total.clone()))?;
+    registry.register(Box::new(m.models.clone()))?;
+    registry.register(Box::new(m.workers.clone()))?;
+    Ok(())
+}
+
+#[cfg(feature = "metrics")]
+pub async fn metrics_middleware(req: Request<axum::body::Body>, next: Next) -> Response {
+    let path = req
+        .extensions()
+        .get::<MatchedPath>()
+        .map(|m| m.as_str().to_owned())
+        .unwrap_or_else(|| "unknown".to_owned());
+    let method = req.method().as_str().to_owned();
+    let start = Instant::now();
+    let response = next.run(req).await;
+    let elapsed = start.elapsed().as_secs_f64();
+    let m = &*METRICS;
+    m.requests_total
+        .with_label_values(&[path.as_str(), method.as_str()])
+        .inc();
+    m.request_duration
+        .with_label_values(&[path.as_str()])
+        .observe(elapsed);
+    let status = response.status().as_u16();
+    if status >= 400 {
+        let class = if status < 500 { "4xx" } else { "5xx" };
+        m.errors_total
+            .with_label_values(&[path.as_str(), class])
+            .inc();
+    }
+    response
+}
+
+#[cfg(feature = "metrics")]
+pub fn inc_models() {
+    METRICS.models.inc();
+}
+
+#[cfg(not(feature = "metrics"))]
+pub fn inc_models() {}
+
+#[cfg(feature = "metrics")]
+pub fn inc_workers() {
+    METRICS.workers.inc();
+}
+
+#[cfg(not(feature = "metrics"))]
+pub fn inc_workers() {}
+
+#[cfg(feature = "metrics")]
+pub fn dec_workers() {
+    METRICS.workers.dec();
+}
+
+#[cfg(not(feature = "metrics"))]
+pub fn dec_workers() {}
+
+#[cfg(all(test, feature = "metrics"))]
+mod tests {
+    use super::*;
+    use prometheus::Encoder;
+
+    #[test]
+    fn register_and_encode() {
+        let registry = prometheus::Registry::new();
+        register(&registry).expect("registration should succeed");
+
+        inc_models();
+        inc_workers();
+        inc_workers();
+        dec_workers();
+
+        let encoder = prometheus::TextEncoder::new();
+        let mut buf = Vec::new();
+        encoder.encode(&registry.gather(), &mut buf).unwrap();
+        let output = String::from_utf8(buf).unwrap();
+
+        assert!(output.contains("dynamo_kvindexer_request_duration_seconds"));
+        assert!(output.contains("dynamo_kvindexer_requests_total"));
+        assert!(output.contains("dynamo_kvindexer_errors_total"));
+        assert!(output.contains("dynamo_kvindexer_models 1"));
+        assert!(output.contains("dynamo_kvindexer_workers 1"));
+    }
+}
--- a/lib/kv-router/src/standalone_indexer/mod.rs
+++ b/lib/kv-router/src/standalone_indexer/mod.rs
@@ -3,6 +3,7 @@

 pub mod indexer;
 pub mod listener;
+pub mod metrics;
 pub mod recovery;
 pub mod registry;
 pub mod server;
@@ -97,7 +98,18 @@ pub async fn run_server(config: IndexerConfig) -> anyhow::Result<()> {

    registry.signal_ready();

-    let state = Arc::new(AppState { registry });
+    #[cfg(feature = "metrics")]
+    let prom_registry = {
+        let r = prometheus::Registry::new();
+        metrics::register(&r).expect("failed to register indexer metrics");
+        r
+    };
+
+    let state = Arc::new(AppState {
+        registry,
+        #[cfg(feature = "metrics")]
+        prom_registry,
+    });

    let app = create_router(state);
    let listener = TcpListener::bind(("0.0.0.0", config.port)).await?;

--- a/lib/kv-router/src/standalone_indexer/registry.rs
+++ b/lib/kv-router/src/standalone_indexer/registry.rs
@@ -113,6 +113,7 @@ impl WorkerRegistry {
                block_size,
                "Creating new indexer"
            );
+            super::metrics::inc_models();
            IndexerEntry {
                indexer: create_indexer(block_size, self.num_threads),
                block_size,
@@ -135,13 +136,13 @@ impl WorkerRegistry {

        // Check for duplicate and insert replay endpoint while holding the lock briefly.
        {
-            let mut entry = self
-                .workers
-                .entry(instance_id)
-                .or_insert_with(|| WorkerEntry {
+            let mut entry = self.workers.entry(instance_id).or_insert_with(|| {
+                super::metrics::inc_workers();
+                WorkerEntry {
                    endpoints: HashMap::new(),
                    replay_endpoints: HashMap::new(),
                    cancels: HashMap::new(),
+                }
            });

            if entry.endpoints.contains_key(&dp_rank) {
@@ -211,6 +212,8 @@ impl WorkerRegistry {
            .remove(&instance_id)
            .ok_or_else(|| anyhow::anyhow!("instance {instance_id} not found"))?;

+        super::metrics::dec_workers();
+
        for cancel in entry.cancels.values() {
            cancel.cancel();
        }
@@ -288,6 +291,8 @@ impl WorkerRegistry {
            .remove(&instance_id)
            .ok_or_else(|| anyhow::anyhow!("instance {instance_id} not found"))?;

+        super::metrics::dec_workers();
+
        for cancel in entry.cancels.values() {
            cancel.cancel();
        }

--- a/lib/kv-router/src/standalone_indexer/server.rs
+++ b/lib/kv-router/src/standalone_indexer/server.rs
@@ -9,6 +9,8 @@ use axum::http::StatusCode;
 use axum::response::IntoResponse;
 use axum::routing::{get, post};
 use axum::{Json, Router};
+#[cfg(feature = "metrics")]
+use prometheus::Encoder;
 use serde::{Deserialize, Serialize};

 use crate::protocols::{LocalBlockHash, WorkerId, compute_block_hash_for_seq};
@@ -17,6 +19,8 @@ use super::registry::{IndexerKey, WorkerRegistry};

 pub struct AppState {
    pub registry: WorkerRegistry,
+    #[cfg(feature = "metrics")]
+    pub prom_registry: prometheus::Registry,
 }

 fn default_tenant() -> String {
@@ -363,6 +367,27 @@ async fn dump_events(State(state): State<Arc<AppState>>) -> impl IntoResponse {
    (StatusCode::OK, Json(serde_json::json!(result)))
 }

+async fn handle_health() -> StatusCode {
+    StatusCode::OK
+}
+
+#[cfg(feature = "metrics")]
+async fn handle_metrics(State(state): State<Arc<AppState>>) -> impl IntoResponse {
+    let encoder = prometheus::TextEncoder::new();
+    let mut buf = Vec::new();
+    encoder
+        .encode(&state.prom_registry.gather(), &mut buf)
+        .unwrap();
+    (
+        StatusCode::OK,
+        [(
+            axum::http::header::CONTENT_TYPE,
+            prometheus::TEXT_FORMAT.to_string(),
+        )],
+        buf,
+    )
+}
+
 pub fn create_router(state: Arc<AppState>) -> Router {
    let router = Router::new()
        .route("/register", post(register))
@@ -373,12 +398,27 @@ pub fn create_router(state: Arc<AppState>) -> Router {
        .route("/dump", get(dump_events))
        .route("/register_peer", post(register_peer))
        .route("/deregister_peer", post(deregister_peer))
-        .route("/peers", get(list_peers));
+        .route("/peers", get(list_peers))
+        .route("/health", get(handle_health));

    #[cfg(feature = "test-endpoints")]
    let router = router
        .route("/test/pause_listener", post(test_pause_listener))
        .route("/test/resume_listener", post(test_resume_listener));

-    router.with_state(state)
+    let router = router.with_state(state.clone());
+
+    #[cfg(feature = "metrics")]
+    let router = {
+        let metrics_route = Router::new()
+            .route("/metrics", get(handle_metrics))
+            .with_state(state);
+        router
+            .layer(axum::middleware::from_fn(
+                super::metrics::metrics_middleware,
+            ))
+            .merge(metrics_route)
+    };
+
+    router
 }
--- a/lib/runtime/src/metrics/prometheus_names.rs
+++ b/lib/runtime/src/metrics/prometheus_names.rs
@@ -74,6 +74,9 @@ pub mod name_prefix {

    /// Prefix for tokio runtime metrics
    pub const TOKIO: &str = "dynamo_tokio";
+
+    /// Prefix for standalone KV indexer metrics
+    pub const KVINDEXER: &str = "dynamo_kvindexer";
 }

 /// Automatically inserted Prometheus label names used across the metrics system
@@ -519,6 +522,24 @@ pub mod tokio_perf {
    pub const ALIVE_TASKS: &str = "alive_tasks";
 }

+/// Standalone KV indexer HTTP service metrics
+pub mod kvindexer {
+    /// HTTP request latency
+    pub const REQUEST_DURATION_SECONDS: &str = "request_duration_seconds";
+
+    /// Total HTTP requests
+    pub const REQUESTS_TOTAL: &str = "requests_total";
+
+    /// HTTP error responses (4xx/5xx)
+    pub const ERRORS_TOTAL: &str = "errors_total";
+
+    /// Number of active model+tenant indexers
+    pub const MODELS: &str = "models";
+
+    /// Number of registered worker instances
+    pub const WORKERS: &str = "workers";
+}
+
 // KvRouter (including KvIndexer) Prometheus metric names
 pub mod kvrouter {
    /// Number of KV cache events applied to the index (including status)