From eacfdb2451bebb50ad7535ab7a6ccfbaac4cc9de Mon Sep 17 00:00:00 2001
From: SimpleTest <simpletestxxx@gmail.com>
Date: Mon, 20 Jul 2026 04:36:20 +0300
Subject: [PATCH] test: measure database load and pool pressure

---
 README.md                                     |  16 +
 compose.load.yaml                             |  11 +
 docs/performance.md                           |  78 ++++
 lib/who_need_help/help.ex                     |   2 +-
 lib/who_need_help_web/telemetry.ex            |  25 ++
 scripts/load-run.sh                           | 390 ++++++++++++++++++
 scripts/quality.sh                            |   5 +
 scripts/rotate-load-metrics-token.sh          |  38 ++
 test/who_need_help/mutual_aid_flow_test.exs   |  15 +
 .../controllers/metrics_controller_test.exs   |   4 +
 10 files changed, 583 insertions(+), 1 deletion(-)
 create mode 100755 scripts/rotate-load-metrics-token.sh

diff --git a/README.md b/README.md
index 895101d..adf9223 100644
--- a/README.md
+++ b/README.md
@@ -231,6 +231,22 @@ The same external-service protocol drill used by CI can be run independently:
 ./scripts/external-boundaries-run.sh local-boundaries
 ```
 
+Run the isolated HTTP/WebSocket/authenticated chat/tracking load profile with
+resource, PostgreSQL statement, database-connection, and Ecto pool-wait
+measurements:
+
+```bash
+./scripts/load-stack-up.sh
+./scripts/load-run.sh local-load
+./scripts/load-stack-stop.sh
+```
+
+The profile has its own generated mode-`0600` environment, Compose project,
+and PostgreSQL volume. It does not use or mutate the ordinary public Compose
+database. Exact inputs and threshold-free evidence are retained below
+`output/performance/local-load/`; see
+[Performance measurement](docs/performance.md) for scope and interpretation.
+
 The cursor-pagination database benchmark also creates a one-run Compose
 project, random database credentials, and a separate PostgreSQL volume:
 
diff --git a/compose.load.yaml b/compose.load.yaml
index 2fb4515..62400e8 100644
--- a/compose.load.yaml
+++ b/compose.load.yaml
@@ -1,4 +1,15 @@
 services:
+  db:
+    # Query-level statistics are enabled only for the isolated load profile.
+    # PostgreSQL requires pg_stat_statements in shared_preload_libraries and a
+    # server restart; the ordinary Compose database is not changed.
+    command:
+      - postgres
+      - -c
+      - shared_preload_libraries=pg_stat_statements
+      - -c
+      - compute_query_id=on
+
   proxy:
     networks:
       edge:
diff --git a/docs/performance.md b/docs/performance.md
index 7a71424..2562606 100644
--- a/docs/performance.md
+++ b/docs/performance.md
@@ -97,11 +97,24 @@ Each run writes ignored evidence below `output/performance/<label>/`:
   stack container, plus a threshold-free CPU/RAM/PID JSON summary;
 - read-only PostgreSQL database size and `pg_stat_database` snapshots before
   and after k6, plus their machine-readable counter deltas;
+- `pg_stat_statements` rankings by total, mean, and maximum execution time,
+  including calls, rows, buffer activity, temporary blocks, and WAL activity;
+- periodic `pg_stat_activity` connection samples with configured pool slots,
+  observed connection headroom, transaction state, lock waits, and named
+  active wait events;
+- per-web Ecto telemetry deltas separating database execution, pool queue, and
+  result decode time;
 - before/after application table counts, exact authenticated-write evidence,
   fixture cleanup output, and a cleanup diff;
 - final Compose state, readiness response, application logs, and cross-node
   PubSub result.
 
+The load-only PostgreSQL command preloads `pg_stat_statements` and creates the
+extension only in the isolated load database. The application exposes
+cumulative Ecto measurements through its authenticated metrics endpoint; the
+runner snapshots every web replica before and after k6 and records the delta.
+Neither mechanism changes the ordinary public Compose database.
+
 Before k6 starts, the production-compiled fixture task verifies the exact
 configured load database name and a deliberate confirmation marker. It creates
 isolated requester/helper/request/assignment pairs through the application
@@ -217,6 +230,71 @@ Ignored evidence:
 
 - `output/performance/final-load-20260719a/`
 
+## Observed SQL and connection-pool run
+
+Observed on 2026-07-20 with 3 web replicas, 2 worker replicas, PostgreSQL 18.4,
+40 paced public HTTP VUs, 40 Phoenix heartbeat VUs, and 8 authenticated
+mutual-aid VUs for 30 seconds.
+
+| Observation | Result |
+| --- | ---: |
+| HTTP requests / failures | 38,429 / 0 |
+| Public checks | 35,163 / 35,163 passed |
+| HTTP duration average / p95 / maximum | 2.42 / 7.74 / 187.11 ms |
+| Authenticated chat/tracking chains | 1,664 |
+| Phoenix heartbeat opened / replies | 240 / 240 |
+| Configured Ecto Repo pool slots | 50 |
+| Peak PostgreSQL client backends | 55 |
+| Minimum observed non-reserved connection headroom | 42 |
+| Idle-in-transaction / lock-waiting backends | 0 / 0 |
+| Ecto average execution / queue / decode time | 308.58 / 31.15 / 0.27 µs |
+| PostgreSQL rollback / deadlock / conflict / temp files | 0 / 0 / 0 / 0 |
+
+The connection sampler observed active PostgreSQL waits named
+`Client:ClientRead` and `IO:WalSync`; it observed no lock wait or
+idle-in-transaction backend. The Ecto queue
+measurement is the application-side evidence for time waiting to check out a
+Repo connection. It averaged 31.15 microseconds over 166,459 queries across
+the three web replicas. This short run did not produce a connection timeout or
+establish a maximum connection capacity.
+
+The SQL ranking exposed an unbounded preload of every message attached to a
+request even though the LiveView immediately loaded a separate 50-message
+cursor page. In the before run that redundant statement executed 3,318 times,
+returned 342,378 rows in aggregate, and consumed 392.378 ms of PostgreSQL
+execution time. The request preload was removed and a regression test now
+requires the chat association to remain unloaded. In the repeat run the
+unbounded statement was absent; the bounded cursor statement retained its
+`LIMIT`, executed 3,328 times, returned 148,512 rows, and averaged 0.122 ms.
+
+No normalized statement in the repeat run used temporary blocks. The largest
+mean statement time was 0.481 ms for six session-token inserts; the
+highest-call request lookup averaged 0.031 ms over 39,936 calls. These are
+observations against the small generated load dataset, not proof that every
+query remains fast at arbitrary data size. The separate 50,000-row database
+profile below checks the indexed list and cursor queries at a larger
+cardinality.
+
+Across the seven measured application/database/proxy containers, simultaneous
+memory samples totalled 1,501.60–1,509.86 MiB during this run. This excludes
+the host OS, the k6 generator, Mailpit, and optional observability services.
+Therefore it is not a claim that this 3-web/2-worker topology fits a 1 GiB or
+2 GiB server. It does show that the measured workload used about 1.47 GiB for
+those seven containers rather than the former kind port-table failure's
+roughly 10 GiB.
+
+The run created exactly 1,664 messages, tracking sessions, and tracking
+samples, plus 8 session tokens; explicit tracking stop left zero current
+positions. Cleanup restored every tracked application-table count, readiness
+and the five-node PubSub probe passed, and the captured application log had no
+database timeout, Postgrex error, deadlock, `ERROR`, `FATAL`, or `PANIC`
+match.
+
+Ignored before/after evidence:
+
+- `output/performance/pool-sql-final-20260720/`
+- `output/performance/pool-sql-chat-fixed-canonical-20260720/`
+
 ## Observed 10-minute authenticated soak
 
 Observed on 2026-07-19 with the same 3-web/2-worker topology and the same
diff --git a/lib/who_need_help/help.ex b/lib/who_need_help/help.ex
index 43ebfb2..ed56737 100644
--- a/lib/who_need_help/help.ex
+++ b/lib/who_need_help/help.ex
@@ -110,7 +110,7 @@ defmodule WhoNeedHelp.Help do
     |> Repo.preload([
       :category,
       requester: :social_identities,
-      assignment: [helper: :social_identities, messages: :sender]
+      assignment: [helper: :social_identities]
     ])
   end
 
diff --git a/lib/who_need_help_web/telemetry.ex b/lib/who_need_help_web/telemetry.ex
index dad868e..f8f8d30 100644
--- a/lib/who_need_help_web/telemetry.ex
+++ b/lib/who_need_help_web/telemetry.ex
@@ -60,6 +60,31 @@ defmodule WhoNeedHelpWeb.Telemetry do
         end,
         description: "Cumulative database query duration"
       ),
+      sum("who_need_help.database.query.execution.duration.microseconds.total",
+        event_name: [:who_need_help, :repo, :query],
+        measurement: fn measurements ->
+          System.convert_time_unit(measurements.query_time, :native, :microsecond)
+        end,
+        description: "Cumulative database execution duration"
+      ),
+      sum("who_need_help.database.query.queue.duration.microseconds.total",
+        event_name: [:who_need_help, :repo, :query],
+        measurement: fn measurements ->
+          measurements
+          |> Map.get(:queue_time, 0)
+          |> System.convert_time_unit(:native, :microsecond)
+        end,
+        description: "Cumulative time waiting for a database connection"
+      ),
+      sum("who_need_help.database.query.decode.duration.microseconds.total",
+        event_name: [:who_need_help, :repo, :query],
+        measurement: fn measurements ->
+          measurements
+          |> Map.get(:decode_time, 0)
+          |> System.convert_time_unit(:native, :microsecond)
+        end,
+        description: "Cumulative database result decoding duration"
+      ),
       counter("who_need_help.websocket.connections.total",
         event_name: [:phoenix, :socket_connected],
         measurement: :duration,
diff --git a/scripts/load-run.sh b/scripts/load-run.sh
index 2afa565..9aa8a4e 100755
--- a/scripts/load-run.sh
+++ b/scripts/load-run.sh
@@ -122,8 +122,123 @@ chmod 700 "$ROOT/output" "$ROOT/output/performance" "$output_dir"
 run_started_at=$(date -u +%Y-%m-%dT%H:%M:%SZ)
 running_marker="$output_dir/.sampling"
 resource_log="$output_dir/docker-stats.jsonl"
+connection_log="$output_dir/database-connections.jsonl"
 touch "$running_marker"
 
+database_psql() {
+  # The variables below are intentionally expanded inside the database container.
+  # shellcheck disable=SC2016
+  "${compose[@]}" exec -T db sh -c \
+    'psql --no-psqlrc --quiet --tuples-only --no-align --set ON_ERROR_STOP=1 \
+      --username "$POSTGRES_USER" --dbname "$POSTGRES_DB"'
+}
+
+prepare_statement_stats() {
+  local preloaded
+  preloaded=$(database_psql <<'SQL'
+SELECT current_setting('shared_preload_libraries')
+  ~ '(^|,)pg_stat_statements(,|$)';
+SQL
+  )
+
+  if [[ "$preloaded" != "t" ]]; then
+    echo "pg_stat_statements is not present in shared_preload_libraries." >&2
+    exit 1
+  fi
+
+  database_psql >"$output_dir/statement-statistics-setup.txt" <<'SQL'
+SELECT current_setting('shared_preload_libraries');
+CREATE EXTENSION IF NOT EXISTS pg_stat_statements;
+SQL
+}
+
+reset_statement_stats() {
+  database_psql >"$output_dir/statement-statistics-reset.txt" <<'SQL'
+SELECT pg_stat_statements_reset();
+SQL
+}
+
+snapshot_statement_stats() {
+  local destination=$1
+
+  database_psql >"$destination" <<'SQL'
+WITH statements AS (
+  SELECT
+    queryid::text AS query_id,
+    regexp_replace(query, '[[:space:]]+', ' ', 'g') AS query,
+    calls,
+    rows,
+    round(total_exec_time::numeric, 3) AS total_exec_time_ms,
+    round(mean_exec_time::numeric, 3) AS mean_exec_time_ms,
+    round(max_exec_time::numeric, 3) AS max_exec_time_ms,
+    shared_blks_hit,
+    shared_blks_read,
+    shared_blks_dirtied,
+    shared_blks_written,
+    temp_blks_read,
+    temp_blks_written,
+    wal_records,
+    wal_fpi,
+    wal_bytes
+  FROM pg_stat_statements
+  WHERE dbid = (SELECT oid FROM pg_database WHERE datname = current_database())
+    AND query NOT LIKE '%pg_stat_statements%'
+    AND query NOT LIKE '%pg_stat_activity%'
+    AND query NOT LIKE '%pg_stat_database%'
+),
+top_total AS (
+  SELECT *
+  FROM statements
+  ORDER BY total_exec_time_ms DESC, query_id
+  LIMIT 25
+),
+top_mean AS (
+  SELECT *
+  FROM statements
+  ORDER BY mean_exec_time_ms DESC, query_id
+  LIMIT 25
+),
+top_max AS (
+  SELECT *
+  FROM statements
+  ORDER BY max_exec_time_ms DESC, query_id
+  LIMIT 25
+)
+SELECT jsonb_pretty(
+  jsonb_build_object(
+    'captured_at', clock_timestamp(),
+    'measurement', 'pg_stat_statements since the pre-load reset',
+    'statement_count', (SELECT count(*) FROM statements),
+    'statistics_info', (SELECT to_jsonb(info) FROM pg_stat_statements_info AS info),
+    'top_by_total_execution_time',
+      (SELECT coalesce(
+        jsonb_agg(
+          to_jsonb(item)
+          ORDER BY total_exec_time_ms DESC, query_id
+        ),
+        '[]'::jsonb
+      ) FROM top_total AS item),
+    'top_by_mean_execution_time',
+      (SELECT coalesce(
+        jsonb_agg(
+          to_jsonb(item)
+          ORDER BY mean_exec_time_ms DESC, query_id
+        ),
+        '[]'::jsonb
+      ) FROM top_mean AS item),
+    'top_by_max_execution_time',
+      (SELECT coalesce(
+        jsonb_agg(
+          to_jsonb(item)
+          ORDER BY max_exec_time_ms DESC, query_id
+        ),
+        '[]'::jsonb
+      ) FROM top_max AS item)
+  )
+);
+SQL
+}
+
 snapshot_database() {
   local destination=$1
 
@@ -246,6 +361,271 @@ summarize_resources() {
       /output/resource-summary.json
 }
 
+sample_database_connections() {
+  database_psql >>"$connection_log" <<'SQL'
+WITH activity AS (
+  SELECT *
+  FROM pg_stat_activity
+  WHERE backend_type = 'client backend'
+    AND pid <> pg_backend_pid()
+),
+active_wait_events AS (
+  SELECT
+    concat_ws(':', wait_event_type, wait_event) AS event,
+    count(*) AS backends
+  FROM activity
+  WHERE state = 'active'
+    AND wait_event IS NOT NULL
+  GROUP BY wait_event_type, wait_event
+)
+SELECT json_build_object(
+  'captured_at', clock_timestamp(),
+  'max_connections', current_setting('max_connections')::integer,
+  'reserved_connections',
+    current_setting('reserved_connections')::integer,
+  'superuser_reserved_connections',
+    current_setting('superuser_reserved_connections')::integer,
+  'client_backends',
+    count(*),
+  'active_backends',
+    count(*) FILTER (WHERE state = 'active'),
+  'idle_backends',
+    count(*) FILTER (WHERE state = 'idle'),
+  'idle_in_transaction_backends',
+    count(*) FILTER (WHERE state = 'idle in transaction'),
+  'active_waiting_backends',
+    count(*) FILTER (
+      WHERE state = 'active'
+        AND wait_event IS NOT NULL
+    ),
+  'lock_waiting_backends',
+    count(*) FILTER (WHERE wait_event_type = 'Lock'),
+  'active_wait_events',
+    (
+      SELECT coalesce(json_object_agg(event, backends), '{}'::json)
+      FROM active_wait_events
+    ),
+  'longest_idle_in_transaction_ms',
+    coalesce(
+      max(
+        extract(epoch FROM clock_timestamp() - xact_start) * 1000
+      ) FILTER (
+        WHERE state = 'idle in transaction'
+      ),
+      0
+    ),
+  'longest_active_query_ms',
+    coalesce(
+      max(
+        extract(epoch FROM clock_timestamp() - query_start) * 1000
+      ) FILTER (
+        WHERE state = 'active'
+      ),
+      0
+    )
+)
+FROM activity;
+SQL
+}
+
+summarize_database_connections() {
+  jq -s \
+    --argjson pool_size "$POOL_SIZE" \
+    --argjson app_replicas "$((LOAD_WEB_REPLICAS + LOAD_WORKER_REPLICAS))" '
+      . as $samples |
+      {
+        schema_version: 1,
+        measurement: "read-only pg_stat_activity samples during the k6 run",
+        thresholds_applied: false,
+        sample_count: length,
+        configured_app_replicas: $app_replicas,
+        configured_pool_size_per_replica: $pool_size,
+        configured_repo_pool_slots: ($app_replicas * $pool_size),
+        max_connections: (map(.max_connections) | max),
+        reserved_connections: (map(.reserved_connections) | max),
+        superuser_reserved_connections:
+          (map(.superuser_reserved_connections) | max),
+        peak_client_backends: (map(.client_backends) | max),
+        peak_active_backends: (map(.active_backends) | max),
+        peak_idle_backends: (map(.idle_backends) | max),
+        peak_idle_in_transaction_backends:
+          (map(.idle_in_transaction_backends) | max),
+        peak_active_waiting_backends:
+          (map(.active_waiting_backends) | max),
+        peak_lock_waiting_backends: (map(.lock_waiting_backends) | max),
+        observed_active_wait_events:
+          ([
+            $samples[]
+            | .active_wait_events
+            | to_entries[]
+          ]
+          | group_by(.key)
+          | map({
+              event: .[0].key,
+              peak_backends: (map(.value) | max),
+              observed_samples: length
+            })),
+        longest_observed_idle_in_transaction_ms:
+          (map(.longest_idle_in_transaction_ms | tonumber) | max),
+        longest_observed_active_query_ms:
+          (map(.longest_active_query_ms | tonumber) | max),
+        minimum_observed_connection_headroom:
+          ((map(
+             .max_connections -
+             .reserved_connections -
+             .superuser_reserved_connections
+           ) | min) -
+           (map(.client_backends) | max))
+      }
+    ' "$connection_log" >"$output_dir/database-connections-summary.json"
+}
+
+prometheus_value() {
+  local metric=$1
+
+  awk -v metric="$metric" '$1 == metric { print $2; found = 1 }
+    END { if (!found) print 0 }'
+}
+
+snapshot_web_metrics() {
+  local destination=$1
+  local temporary
+  temporary=$(mktemp "${TMPDIR:-/tmp}/wnh-load-metrics.XXXXXX")
+  : >"$temporary"
+
+  for container in "${web_containers[@]}"; do
+    local scrape node queries total execution queue decode
+    scrape=$(
+      docker exec "$container" sh -c \
+        'curl --fail --silent --show-error \
+          --header "Authorization: Bearer $METRICS_TOKEN" \
+          --header "X-Forwarded-Proto: https" \
+          --header "Host: $PHX_HOST" \
+          http://127.0.0.1:4000/metrics'
+    )
+    node=$(
+      docker exec "$container" /app/bin/who_need_help rpc \
+        'IO.puts(JSON.encode!(%{node: to_string(node())}))' |
+        tail -n 1 |
+        jq -r '.node'
+    )
+    queries=$(
+      printf '%s\n' "$scrape" |
+        prometheus_value who_need_help_database_queries_total
+    )
+    total=$(
+      printf '%s\n' "$scrape" |
+        prometheus_value who_need_help_database_query_duration_microseconds_total
+    )
+    execution=$(
+      printf '%s\n' "$scrape" |
+        prometheus_value \
+          who_need_help_database_query_execution_duration_microseconds_total
+    )
+    queue=$(
+      printf '%s\n' "$scrape" |
+        prometheus_value \
+          who_need_help_database_query_queue_duration_microseconds_total
+    )
+    decode=$(
+      printf '%s\n' "$scrape" |
+        prometheus_value \
+          who_need_help_database_query_decode_duration_microseconds_total
+    )
+
+    jq -cn \
+      --arg container "$container" \
+      --arg node "$node" \
+      --argjson queries "$queries" \
+      --argjson total_duration_us "$total" \
+      --argjson execution_duration_us "$execution" \
+      --argjson queue_duration_us "$queue" \
+      --argjson decode_duration_us "$decode" \
+      '{
+        container: $container,
+        node: $node,
+        queries: $queries,
+        total_duration_us: $total_duration_us,
+        execution_duration_us: $execution_duration_us,
+        queue_duration_us: $queue_duration_us,
+        decode_duration_us: $decode_duration_us
+      }' >>"$temporary"
+  done
+
+  jq -s 'sort_by(.node)' "$temporary" >"$destination"
+  rm -f "$temporary"
+}
+
+summarize_web_metrics() {
+  local before=$1
+  local after=$2
+
+  jq -n \
+    --slurpfile before "$before" \
+    --slurpfile after "$after" '
+      [
+        $after[0][] as $after_row
+        | ($before[0][] | select(.node == $after_row.node)) as $before_row
+        | {
+            node: $after_row.node,
+            queries: ($after_row.queries - $before_row.queries),
+            total_duration_us:
+              ($after_row.total_duration_us - $before_row.total_duration_us),
+            execution_duration_us:
+              ($after_row.execution_duration_us -
+               $before_row.execution_duration_us),
+            queue_duration_us:
+              ($after_row.queue_duration_us - $before_row.queue_duration_us),
+            decode_duration_us:
+              ($after_row.decode_duration_us - $before_row.decode_duration_us)
+          }
+        | . + {
+            average_total_duration_us:
+              (if .queries > 0 then .total_duration_us / .queries else 0 end),
+            average_execution_duration_us:
+              (if .queries > 0 then .execution_duration_us / .queries else 0 end),
+            average_queue_duration_us:
+              (if .queries > 0 then .queue_duration_us / .queries else 0 end),
+            average_decode_duration_us:
+              (if .queries > 0 then .decode_duration_us / .queries else 0 end)
+          }
+      ] as $nodes
+      | {
+          schema_version: 1,
+          measurement:
+            "per-web Ecto telemetry counter deltas around the k6 run",
+          thresholds_applied: false,
+          nodes: $nodes,
+          cluster: (
+            reduce $nodes[] as $node
+              ({
+                queries: 0,
+                total_duration_us: 0,
+                execution_duration_us: 0,
+                queue_duration_us: 0,
+                decode_duration_us: 0
+              };
+               .queries += $node.queries |
+               .total_duration_us += $node.total_duration_us |
+               .execution_duration_us += $node.execution_duration_us |
+               .queue_duration_us += $node.queue_duration_us |
+               .decode_duration_us += $node.decode_duration_us)
+            | . + {
+                average_total_duration_us:
+                  (if .queries > 0 then .total_duration_us / .queries else 0 end),
+                average_execution_duration_us:
+                  (if .queries > 0
+                   then .execution_duration_us / .queries else 0 end),
+                average_queue_duration_us:
+                  (if .queries > 0 then .queue_duration_us / .queries else 0 end),
+                average_decode_duration_us:
+                  (if .queries > 0 then .decode_duration_us / .queries else 0 end)
+              }
+          )
+        }
+    ' >"$output_dir/ecto-query-metrics-summary.json"
+}
+
 run_fixture_tool() {
   local action=$1
 
@@ -317,6 +697,7 @@ sample_resources() {
     docker stats --no-stream --format '{{json .}}' "${measured_containers[@]}" |
       jq -c --arg observed_at "$observed_at" '. + {ObservedAt: $observed_at}' \
         >>"$resource_log"
+    sample_database_connections
     sleep 1
   done
 }
@@ -378,11 +759,14 @@ trap cleanup_on_exit EXIT HUP INT TERM
   uname -a
 } >"$output_dir/environment.txt"
 
+prepare_statement_stats
 snapshot_database "$output_dir/database-pre-fixtures.txt"
 run_fixture_tool prepare >"$output_dir/fixture-prepare.log" 2>&1
 fixtures_prepared=true
 snapshot_database "$output_dir/database-before-load.txt"
 snapshot_database_metrics "$output_dir/database-metrics-before-load.json"
+reset_statement_stats
+snapshot_web_metrics "$output_dir/ecto-query-metrics-before.json"
 sample_resources &
 sampler_pid=$!
 
@@ -419,6 +803,12 @@ set -e
 cleanup_sampler
 sampler_pid=
 summarize_resources
+summarize_database_connections
+snapshot_web_metrics "$output_dir/ecto-query-metrics-after.json"
+summarize_web_metrics \
+  "$output_dir/ecto-query-metrics-before.json" \
+  "$output_dir/ecto-query-metrics-after.json"
+snapshot_statement_stats "$output_dir/statement-statistics.json"
 
 snapshot_database "$output_dir/database-after-load.txt"
 snapshot_database_metrics "$output_dir/database-metrics-after-load.json"
diff --git a/scripts/quality.sh b/scripts/quality.sh
index 564e3e6..cec7b96 100755
--- a/scripts/quality.sh
+++ b/scripts/quality.sh
@@ -85,6 +85,11 @@ REHEARSAL_IMAGE=who-need-help:rehearsal-render \
   -f compose.yaml -f compose.upgrade-rehearsal.yaml config --quiet
 docker compose --env-file .env.load.example \
   -f compose.yaml -f compose.load.yaml config --quiet
+test "$(
+  docker compose --env-file .env.load.example \
+    -f compose.yaml -f compose.load.yaml config --format json |
+    jq -r '.services.db.command | join(" ")'
+)" = "postgres -c shared_preload_libraries=pg_stat_statements -c compute_query_id=on"
 mkdir -p "$scan_dir/observability-runtime/prometheus" \
   "$scan_dir/observability-runtime/grafana"
 OBSERVABILITY_RUNTIME_DIR="$scan_dir/observability-runtime" \
diff --git a/scripts/rotate-load-metrics-token.sh b/scripts/rotate-load-metrics-token.sh
new file mode 100755
index 0000000..5883a2a
--- /dev/null
+++ b/scripts/rotate-load-metrics-token.sh
@@ -0,0 +1,38 @@
+#!/bin/sh
+set -eu
+
+ROOT=$(CDPATH='' cd -- "$(dirname -- "$0")/.." && pwd)
+ENV_FILE="$ROOT/.env.load"
+
+if [ ! -f "$ENV_FILE" ]; then
+  echo "Missing $ENV_FILE. Run scripts/ensure-local-load-env.sh first." >&2
+  exit 1
+fi
+
+for command in openssl perl; do
+  if ! command -v "$command" >/dev/null 2>&1; then
+    echo "Required command is unavailable: $command" >&2
+    exit 1
+  fi
+done
+
+new_metrics_token=$(openssl rand -hex 32)
+temporary=$(mktemp "${ENV_FILE}.rotate.XXXXXX")
+trap 'rm -f "$temporary"' EXIT HUP INT TERM
+chmod 600 "$temporary"
+
+NEW_METRICS_TOKEN=$new_metrics_token \
+  perl -pe '
+    s/^METRICS_TOKEN=.*/METRICS_TOKEN=$ENV{NEW_METRICS_TOKEN}/;
+  ' "$ENV_FILE" >"$temporary"
+
+if cmp -s "$ENV_FILE" "$temporary"; then
+  echo "METRICS_TOKEN is missing from $ENV_FILE." >&2
+  exit 1
+fi
+
+mv "$temporary" "$ENV_FILE"
+chmod 600 "$ENV_FILE"
+trap - EXIT HUP INT TERM
+
+echo "The isolated load-profile metrics token was rotated without printing it."
diff --git a/test/who_need_help/mutual_aid_flow_test.exs b/test/who_need_help/mutual_aid_flow_test.exs
index 77dee7a..5f9e754 100644
--- a/test/who_need_help/mutual_aid_flow_test.exs
+++ b/test/who_need_help/mutual_aid_flow_test.exs
@@ -83,6 +83,21 @@ defmodule WhoNeedHelp.MutualAidFlowTest do
              Messaging.send_message(outsider_scope, assignment, %{"body" => "not allowed"})
   end
 
+  test "request details do not preload the unbounded chat history", context do
+    {:ok, request} = Help.create_request(context.requester_scope, context.request_attrs)
+    {:ok, assignment} = Help.accept_request(context.helper_scope, request.id)
+
+    {:ok, _message} =
+      Messaging.send_message(context.helper_scope, assignment, %{"body" => "Bounded separately"})
+
+    loaded_request = Help.get_request!(request.id)
+
+    assert %Ecto.Association.NotLoaded{} = loaded_request.assignment.messages
+
+    assert [%{body: "Bounded separately"}] =
+             Messaging.list_messages(context.requester_scope, loaded_request.assignment)
+  end
+
   test "request discovery uses stable cursor pages without gaps or duplicates", context do
     requests =
       for offset <- 1..5 do
diff --git a/test/who_need_help_web/controllers/metrics_controller_test.exs b/test/who_need_help_web/controllers/metrics_controller_test.exs
index f52ebf0..8d29d1a 100644
--- a/test/who_need_help_web/controllers/metrics_controller_test.exs
+++ b/test/who_need_help_web/controllers/metrics_controller_test.exs
@@ -20,6 +20,7 @@ defmodule WhoNeedHelpWeb.MetricsControllerTest do
 
   test "exports Prometheus metrics for the configured bearer token", %{conn: conn} do
     get(conn, "/healthz/live")
+    WhoNeedHelp.Repo.query!("SELECT 1")
 
     conn =
       conn
@@ -36,5 +37,8 @@ defmodule WhoNeedHelpWeb.MetricsControllerTest do
     assert body =~ "# TYPE who_need_help_http_requests_total counter"
     assert body =~ "who_need_help_http_requests_total "
     assert body =~ "who_need_help_http_request_duration_microseconds_total "
+    assert body =~ "who_need_help_database_query_execution_duration_microseconds_total "
+    assert body =~ "who_need_help_database_query_queue_duration_microseconds_total "
+    assert body =~ "who_need_help_database_query_decode_duration_microseconds_total "
   end
 end