diff --git a/dashboard/pages/fragment_graph.tsx b/dashboard/pages/fragment_graph.tsx
index e5179e69fdce4..926ed767b93ee 100644
--- a/dashboard/pages/fragment_graph.tsx
+++ b/dashboard/pages/fragment_graph.tsx
@@ -45,10 +45,6 @@ import {
   calculateBPRate,
   getActorBackPressures,
   getBackPressureWithoutPrometheus,
-  p50,
-  p90,
-  p95,
-  p99,
 } from "../lib/api/metric"
 import { getFragments, getStreamingJobs } from "../lib/api/streaming"
 import { FragmentBox } from "../lib/layout"
@@ -179,9 +175,6 @@ function buildFragmentDependencyAsEdges(
 
 const SIDEBAR_WIDTH = 200
 
-type BackPressureAlgo = "p50" | "p90" | "p95" | "p99"
-const backPressureAlgos: BackPressureAlgo[] = ["p50", "p90", "p95", "p99"]
-
 type BackPressureDataSource = "Embedded" | "Prometheus"
 const backPressureDataSources: BackPressureDataSource[] = [
   "Embedded",
@@ -193,16 +186,15 @@ export default function Streaming() {
   const { response: fragmentList } = useFetch(getFragments)
 
   const [relationId, setRelationId] = useQueryState("id", parseAsInteger)
-  const [backPressureAlgo, setBackPressureAlgo] = useQueryState("backPressure")
   const [selectedFragmentId, setSelectedFragmentId] = useState<number>()
   // used to get the data source
-  const [backPressureDataSourceAlgo, setBackPressureDataSourceAlgo] =
-    useState("Embedded")
+  const [backPressureDataSource, setBackPressureDataSource] =
+    useState<BackPressureDataSource>("Embedded")
 
   const { response: actorBackPressures } = useFetch(
     getActorBackPressures,
     INTERVAL,
-    backPressureDataSourceAlgo === "Prometheus" && backPressureAlgo !== null
+    backPressureDataSource === "Prometheus"
   )
 
   const fragmentDependencyCallback = useCallback(() => {
@@ -234,6 +226,8 @@ export default function Streaming() {
   }, [relationId, relationList, setRelationId])
 
   // get back pressure rate without prometheus
+  // TODO(bugen): extract the following logic to a hook and unify the interface
+  // with Prometheus data source.
   const [backPressuresMetricsWithoutPromtheus, setBackPressuresMetrics] =
     useState<BackPressuresMetrics>()
   const [previousBP, setPreviousBP] = useState<BackPressureInfo[]>([])
@@ -241,7 +235,7 @@ export default function Streaming() {
   const toast = useErrorToast()
 
   useEffect(() => {
-    if (backPressureDataSourceAlgo === "Embedded") {
+    if (backPressureDataSource === "Embedded") {
       const interval = setInterval(() => {
         const fetchNewBP = async () => {
           const newBP = await getBackPressureWithoutPrometheus()
@@ -253,7 +247,7 @@ export default function Streaming() {
       }, INTERVAL)
       return () => clearInterval(interval)
     }
-  }, [currentBP, backPressureDataSourceAlgo])
+  }, [currentBP, backPressureDataSource])
 
   useEffect(() => {
     if (currentBP !== null && previousBP !== null) {
@@ -330,14 +324,11 @@ export default function Streaming() {
   }
 
   const backPressures = useMemo(() => {
-    if (
-      (actorBackPressures && backPressureAlgo && backPressureAlgo) ||
-      backPressuresMetricsWithoutPromtheus
-    ) {
+    if (actorBackPressures || backPressuresMetricsWithoutPromtheus) {
       let map = new Map()
 
       if (
-        backPressureDataSourceAlgo === "Embedded" &&
+        backPressureDataSource === "Embedded" &&
         backPressuresMetricsWithoutPromtheus
       ) {
         for (const m of backPressuresMetricsWithoutPromtheus.outputBufferBlockingDuration) {
@@ -347,41 +338,32 @@ export default function Streaming() {
           )
         }
       } else if (
-        backPressureDataSourceAlgo !== "Embedded" &&
+        backPressureDataSource === "Prometheus" &&
         actorBackPressures
       ) {
-        for (const m of actorBackPressures.outputBufferBlockingDuration) {
-          let algoFunc
-          switch (backPressureAlgo) {
-            case "p50":
-              algoFunc = p50
-              break
-            case "p90":
-              algoFunc = p90
-              break
-            case "p95":
-              algoFunc = p95
-              break
-            case "p99":
-              algoFunc = p99
-              break
-            default:
-              return
+        if (actorBackPressures) {
+          for (const m of actorBackPressures.outputBufferBlockingDuration) {
+            if (m.sample.length > 0) {
+              // Note: We issue an instant query to Prometheus to get the most recent value.
+              // So there should be only one sample here.
+              //
+              // Due to https://github.com/risingwavelabs/risingwave/issues/15280, it's still
+              // possible that an old version of meta service returns a range-query result.
+              // So we take the one with the latest timestamp here.
+              const value = _(m.sample).maxBy((s) => s.timestamp)!.value * 100
+              map.set(
+                `${m.metric.fragment_id}_${m.metric.downstream_fragment_id}`,
+                value
+              )
+            }
           }
-
-          const value = algoFunc(m.sample) * 100
-          map.set(
-            `${m.metric.fragment_id}_${m.metric.downstream_fragment_id}`,
-            value
-          )
         }
       }
       return map
     }
   }, [
-    backPressureDataSourceAlgo,
+    backPressureDataSource,
     actorBackPressures,
-    backPressureAlgo,
     backPressuresMetricsWithoutPromtheus,
   ])
 
@@ -456,9 +438,11 @@ export default function Streaming() {
           <FormControl>
             <FormLabel>Back Pressure Data Source</FormLabel>
             <Select
-              value={backPressureDataSourceAlgo}
+              value={backPressureDataSource}
               onChange={(event) =>
-                setBackPressureDataSourceAlgo(event.target.value)
+                setBackPressureDataSource(
+                  event.target.value as BackPressureDataSource
+                )
               }
             >
               {backPressureDataSources.map((algo) => (
@@ -468,26 +452,6 @@ export default function Streaming() {
               ))}
             </Select>
           </FormControl>
-          {backPressureDataSourceAlgo === "Prometheus" && (
-            <FormControl>
-              <FormLabel>Back Pressure Algorithm</FormLabel>
-              <Select
-                value={backPressureAlgo ?? undefined}
-                onChange={(event) => {
-                  setBackPressureAlgo(event.target.value as BackPressureAlgo)
-                }}
-              >
-                <option value="" disabled selected hidden>
-                  Please select
-                </option>
-                {backPressureAlgos.map((algo) => (
-                  <option value={algo} key={algo}>
-                    {algo}
-                  </option>
-                ))}
-              </Select>
-            </FormControl>
-          )}
           <Flex height="full" width="full" flexDirection="column">
             <Text fontWeight="semibold">Fragments</Text>
             {fragmentDependencyDag && (
diff --git a/src/meta/src/dashboard/prometheus.rs b/src/meta/src/dashboard/prometheus.rs
index 7baade4969749..435dd6896e6e7 100644
--- a/src/meta/src/dashboard/prometheus.rs
+++ b/src/meta/src/dashboard/prometheus.rs
@@ -17,7 +17,7 @@ use std::time::SystemTime;
 
 use anyhow::anyhow;
 use axum::{Extension, Json};
-use prometheus_http_query::response::{RangeVector, Sample};
+use prometheus_http_query::response::{InstantVector, RangeVector, Sample};
 use serde::Serialize;
 
 use super::handlers::{err, DashboardError};
@@ -41,6 +41,7 @@ impl From<&Sample> for PrometheusSample {
 #[derive(Serialize, Debug)]
 pub struct PrometheusVector {
     metric: HashMap<String, String>,
+    // Multiple samples from `RangeVector` or single sample from `InstantVector`.
     sample: Vec<PrometheusSample>,
 }
 
@@ -48,7 +49,16 @@ impl From<&RangeVector> for PrometheusVector {
     fn from(value: &RangeVector) -> Self {
         PrometheusVector {
             metric: value.metric().clone(),
-            sample: value.samples().iter().map(PrometheusSample::from).collect(),
+            sample: value.samples().iter().map(Into::into).collect(),
+        }
+    }
+}
+
+impl From<&InstantVector> for PrometheusVector {
+    fn from(value: &InstantVector) -> Self {
+        PrometheusVector {
+            metric: value.metric().clone(),
+            sample: vec![value.sample().into()],
         }
     }
 }
@@ -134,27 +144,12 @@ pub async fn list_prometheus_fragment_back_pressure(
     Extension(srv): Extension<Service>,
 ) -> Result<Json<FragmentBackPressure>> {
     if let Some(ref client) = srv.prometheus_client {
-        let now = SystemTime::now();
         let back_pressure_query =
             format!("avg(rate(stream_actor_output_buffer_blocking_duration_ns{{{}}}[60s])) by (fragment_id, downstream_fragment_id) / 1000000000", srv.prometheus_selector);
-        let result = client
-            .query_range(
-                back_pressure_query,
-                now.duration_since(SystemTime::UNIX_EPOCH)
-                    .unwrap()
-                    .as_secs() as i64
-                    - 1800,
-                now.duration_since(SystemTime::UNIX_EPOCH)
-                    .unwrap()
-                    .as_secs() as i64,
-                15.0,
-            )
-            .get()
-            .await
-            .map_err(err)?;
+        let result = client.query(back_pressure_query).get().await.map_err(err)?;
         let back_pressure_data = result
             .data()
-            .as_matrix()
+            .as_vector()
             .unwrap()
             .iter()
             .map(PrometheusVector::from)