fix: use proper index when (re)calculating the additional balance

src/Book.ts

@@ -102,6 +102,8 @@ export class Book<U extends ITransaction = ITransaction, J extends IJournal = IJ
       if (balanceSnapshot) {
         // Use cached balance
         parsedQuery._id = { $gt: balanceSnapshot.transaction };
+        // And make sure to use the appropriate (default "_id_") index for the additional balance
+        options.hint = { _id: 1 };
       }
     }
 

src/IOptions.ts

@@ -1,8 +1,9 @@
-import { ClientSession } from "mongoose";
-import { ReadPreferenceLike } from "mongodb";
+import type { ClientSession } from "mongoose";
+import type { ReadPreferenceLike, Hint } from "mongodb";
 
 // aggregate of mongoose expects Record<string, unknown> type
 export type IOptions = {
   session?: ClientSession;
   readPreference?: ReadPreferenceLike;
+  hint?: Hint;
 };