Dictionary data type.

If you’ve ever found yourself stuck in painfully slow loops while processing thousands of records in Business Central, this one’s for you. Any routine that might be dragging through 10,000+ records, switching to Dictionary for caching turns out to be a game-changer.
The Problem
Processing 10,000 sales lines that need customer data. Traditional approach hits the database 10,000 times – one lookup per line.
Result: 16-24 seconds for 10,000 records

The Fix
Use dictionary object to cache
Result: 2-4 seconds for 10,000 records ~ 85% faster.

When to Use Dictionary
Repeated lookups to the same master data
Processing lines with duplicate header references
Cross-reference mappings (old ID — new ID)
Caching calculation results
Stop hitting the database unnecessarily. Let Dictionary be your performance multiplier.