From 3b8d413a087de69e220581a6d84da132e4488dd7 Mon Sep 17 00:00:00 2001
From: Cody <36463298+ugcodrr@users.noreply.github.com>
Date: Wed, 21 Oct 2026 02:42:38 -0400
Subject: [PATCH 1/2] fix(api): save players and sessions to Mongoose as nested
 documents
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PlayerService.saveOne and SessionService.resetPlayer handed Mongoose the
flat serialized document, with keys like "stats.bedwars.overall.wins".
Mongoose casts a replacement by building a document and setting each key,
and its change tracking rescans every modified path on each set, so a save
with K keys cost O(K²): about 100 ms for a player with 3,200 keys.

Passing the same document unflattened avoids that: about 18 ms for that
player, and 6.5 ms instead of 12 ms for an average one. The stored
documents are byte-identical, BSON number types and key order included.

Guild saves keep the flat document. Their cost is casting the members
array, not the dotted keys, so nesting doesn't change it.
---
 apps/api/src/player/player.service.ts   | 7 ++++++-
 apps/api/src/session/session.service.ts | 4 ++--
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/apps/api/src/player/player.service.ts b/apps/api/src/player/player.service.ts
index 0d5ad6218..cb682ed52 100644
--- a/apps/api/src/player/player.service.ts
+++ b/apps/api/src/player/player.service.ts
@@ -11,6 +11,7 @@ import {
   type Circular,
   type Flatten,
   flatten,
+  unflatten,
 } from "@statsify/util";
 import { CacheLevel, StatusNotFoundException } from "@statsify/api-client";
 import { HypixelService } from "#hypixel";
@@ -167,8 +168,12 @@ export class PlayerService {
     const serializedPlayer = serialize<Player>(Player, flatPlayer);
 
     const promises = [
+      // Mongoose gets the nested document: with thousands of dotted keys, its change
+      // tracking makes the replace O(n²)
       this.playerModel
-        .replaceOne({ uuid: player.uuid }, serializedPlayer, { upsert: true })
+        .replaceOne({ uuid: player.uuid }, unflatten(serializedPlayer), {
+          upsert: true,
+        })
         .exec(),
       this.playerLeaderboardService.addLeaderboards(
         Player,
diff --git a/apps/api/src/session/session.service.ts b/apps/api/src/session/session.service.ts
index 384e89041..46f5f7621 100644
--- a/apps/api/src/session/session.service.ts
+++ b/apps/api/src/session/session.service.ts
@@ -11,7 +11,7 @@ import {
   PlayerNotFoundException,
   SessionNotFoundException,
 } from "@statsify/api-client";
-import { type Circular, flatten } from "@statsify/util";
+import { type Circular, flatten, unflatten } from "@statsify/util";
 import { DateTime } from "luxon";
 import {
   Inject,
@@ -59,7 +59,7 @@ export class SessionService {
 
     doc.sessionReset = Math.round(DateTime.now().toMillis() / 1000);
 
-    await this.sessionModel.replaceOne({ uuid: doc.uuid }, doc, { upsert: true }).lean().exec();
+    await this.sessionModel.replaceOne({ uuid: doc.uuid }, unflatten(doc), { upsert: true }).lean().exec();
 
     return deserialize(Player, flatPlayer);
   }

From ea24bf1a5f3b26c8a49b4911f3089d3a614a036c Mon Sep 17 00:00:00 2001
From: Cody <36463298+ugcodrr@users.noreply.github.com>
Date: Thu, 5 Nov 2026 02:58:08 -0500
Subject: [PATCH 2/2] refactor(api): shorten the nested player save comment

---
 apps/api/src/player/player.service.ts | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/apps/api/src/player/player.service.ts b/apps/api/src/player/player.service.ts
index 1614e19bf..91059f65c 100644
--- a/apps/api/src/player/player.service.ts
+++ b/apps/api/src/player/player.service.ts
@@ -177,8 +177,7 @@ export class PlayerService {
     const serializedPlayer = serialize<Player>(Player, flatPlayer);
 
     const promises = [
-      // Mongoose gets the nested document: with thousands of dotted keys, its change
-      // tracking makes the replace O(n²)
+      // Thousands of dotted keys make Mongoose's change tracking O(n²)
       this.playerModel
         .replaceOne({ uuid: player.uuid }, unflatten(serializedPlayer), {
           upsert: true,