From 74ad04abc29b266b929386c7e67ada679509d70b Mon Sep 17 00:00:00 2001
From: Mark Saroufim <marksaroufim@meta.com>
Date: Fri, 6 Feb 2026 21:07:25 -0800
Subject: [PATCH] Add in-memory caching to leaderboard endpoints

Cache responses from /api/leaderboard-summaries and /api/leaderboard/<id>
with a 60-second TTL to avoid running expensive SQL queries on every request.
Follows the same pattern used in the events API.
---
 kernelboard/api/leaderboard.py           | 13 +++++++++++++
 kernelboard/api/leaderboard_summaries.py | 22 +++++++++++++++++++---
 2 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/kernelboard/api/leaderboard.py b/kernelboard/api/leaderboard.py
index 2cb6a20b..42b3988d 100644
--- a/kernelboard/api/leaderboard.py
+++ b/kernelboard/api/leaderboard.py
@@ -1,3 +1,4 @@
+import time
 from typing import Any
 from flask import Blueprint
 from kernelboard.lib.db import get_db_connection
@@ -8,9 +9,18 @@
 
 leaderboard_bp = Blueprint("leaderboard_bp", __name__, url_prefix="/leaderboard")
 
+# Simple in-memory cache keyed by leaderboard_id
+_cache: dict[int, dict] = {}
+CACHE_TTL_SECONDS = 60
+
 
 @leaderboard_bp.route("/<int:leaderboard_id>", methods=["GET"])
 def leaderboard(leaderboard_id: int):
+    now = time.time()
+    cached = _cache.get(leaderboard_id)
+    if cached is not None and (now - cached["timestamp"]) < CACHE_TTL_SECONDS:
+        return http_success(cached["data"])
+
     conn = get_db_connection()
     query = _get_query()
     with conn.cursor() as cur:
@@ -27,6 +37,9 @@ def leaderboard(leaderboard_id: int):
     data = result[0]
 
     res = to_api_leaderboard_item(data)
+
+    _cache[leaderboard_id] = {"data": res, "timestamp": now}
+
     return http_success(res)
 
 
diff --git a/kernelboard/api/leaderboard_summaries.py b/kernelboard/api/leaderboard_summaries.py
index 0144c39c..9417d21b 100644
--- a/kernelboard/api/leaderboard_summaries.py
+++ b/kernelboard/api/leaderboard_summaries.py
@@ -1,3 +1,5 @@
+import time
+
 from flask import Blueprint
 from datetime import datetime, timezone
 from kernelboard.lib.db import get_db_connection
@@ -8,6 +10,13 @@
     "leaderboard_summaries_bp", __name__, url_prefix="/leaderboard-summaries"
 )
 
+# Simple in-memory cache
+_cache = {
+    "data": None,
+    "timestamp": 0,
+}
+CACHE_TTL_SECONDS = 60
+
 
 @leaderboard_summaries_bp.route("", methods=["GET"])
 def index():
@@ -28,6 +37,10 @@ def index():
     #     ],
     # }
 
+    now = time.time()
+    if _cache["data"] is not None and (now - _cache["timestamp"]) < CACHE_TTL_SECONDS:
+        return http_success(_cache["data"])
+
     conn = get_db_connection()
     query = _get_query()
     with conn.cursor() as cur:
@@ -38,9 +51,12 @@ def index():
         if lb["gpu_types"] is None:
             lb["gpu_types"] = []
 
-    return http_success(
-        {"leaderboards": leaderboards, "now": datetime.now(timezone.utc)}
-    )
+    result = {"leaderboards": leaderboards, "now": datetime.now(timezone.utc)}
+
+    _cache["data"] = result
+    _cache["timestamp"] = now
+
+    return http_success(result)
 
 
 def _get_query():