perf: connection pooling, query consolidation, inline chart data, batch milestones

app/routes/leaderboard.py

@@ -2,7 +2,7 @@ from flask import Blueprint, render_template
 from app.auth import login_required
 from app.db import query, query_one
 from app.config import SYDNEY_TZ
-from app.utils import calculate_streak, calculate_weight_change
+from app.utils import calculate_streaks_bulk, calculate_weight_change
 from datetime import timezone
 
 bp = Blueprint("leaderboard", __name__)
@@ -11,23 +11,38 @@ bp = Blueprint("leaderboard", __name__)
 @bp.route("/leaderboard")
 @login_required
 def index():
-    # Get all users with their weight stats
+    # Get all users with weight stats using window functions (no correlated subqueries)
     users = query("""
+        WITH user_weights AS (
+            SELECT
+                user_id,
+                FIRST_VALUE(weight_kg) OVER (PARTITION BY user_id ORDER BY checked_in_at ASC)  AS first_weight,
+                FIRST_VALUE(weight_kg) OVER (PARTITION BY user_id ORDER BY checked_in_at DESC) AS current_weight,
+                COUNT(*)              OVER (PARTITION BY user_id)                               AS total_checkins,
+                MAX(checked_in_at)    OVER (PARTITION BY user_id)                               AS last_checkin,
+                ROW_NUMBER()          OVER (PARTITION BY user_id ORDER BY checked_in_at DESC)   AS rn
+            FROM checkins
+        )
         SELECT
             u.id,
             u.display_name,
             u.username,
             u.starting_weight_kg,
             u.goal_weight_kg,
-            (SELECT weight_kg FROM checkins WHERE user_id = u.id ORDER BY checked_in_at ASC LIMIT 1) as first_weight,
-            (SELECT weight_kg FROM checkins WHERE user_id = u.id ORDER BY checked_in_at DESC LIMIT 1) as current_weight,
-            (SELECT COUNT(*) FROM checkins WHERE user_id = u.id) as total_checkins,
-            (SELECT checked_in_at FROM checkins WHERE user_id = u.id ORDER BY checked_in_at DESC LIMIT 1) as last_checkin
+            uw.first_weight,
+            uw.current_weight,
+            uw.total_checkins,
+            uw.last_checkin
         FROM users u
+        JOIN user_weights uw ON uw.user_id = u.id AND uw.rn = 1
         WHERE u.is_private = FALSE
         ORDER BY u.created_at
     """)
 
+    # Batch-compute streaks for all users in one query
+    user_ids = [u["id"] for u in users]
+    all_streaks = calculate_streaks_bulk(user_ids)
+
     # Calculate rankings
     ranked = []
     for u in users:
@@ -41,7 +56,7 @@ def index():
             total_to_lose = start_w - goal
             goal_progress = min(100, round((weight_lost / total_to_lose) * 100, 1)) if total_to_lose > 0 else 0
 
-        streak = calculate_streak(u["id"])
+        streak = all_streaks.get(u["id"], {"current": 0, "best": 0})
         ranked.append({
             **u,
             "weight_lost": weight_lost,