diff --git a/.changeset/add-accesskey-index.md b/.changeset/add-accesskey-index.md
new file mode 100644
index 0000000000..4a9b44d73c
--- /dev/null
+++ b/.changeset/add-accesskey-index.md
@@ -0,0 +1,5 @@
+---
+"@hyperdx/api": minor
+---
+
+Add unique MongoDB index on accessKey field in User model to eliminate full collection scans during API key authentication. This could cause startup failures if any existing users share duplicate accessKey values.
diff --git a/packages/api/src/models/user.ts b/packages/api/src/models/user.ts
index b7067b20c3..8f60fadeb5 100644
--- a/packages/api/src/models/user.ts
+++ b/packages/api/src/models/user.ts
@@ -47,5 +47,6 @@ UserSchema.plugin(passportLocalMongoose, {
 });
 
 UserSchema.index({ email: 1 }, { unique: true });
+UserSchema.index({ accessKey: 1 }, { unique: true });
 
 export default mongoose.model<IUser>('User', UserSchema);