Direct Lake vS Direct Query

Hi,

I understand why you prefer DirectQuery is very flexible, especially when you need live data or can't move everything into OneLake.

But here's the key difference I've noticed:

- Direct Lake reads directly from Delta tables in OneLake. Then all the transformations, aggregations and joins happens before the report runs, so Power BI just uses pre-optimized data. The report is fast, but requires more ETL work upfront.

- DirectQuery queries the source every single time – warehouse, SQL Server, etc. It's flexible, but the performance depends entirely on how complex your queries and DAX are.

The catch with DirectQuery? If you have:

• Complex joins
• Heavy aggregations
• Lots of concurrent users

Then your warehouse becomes the bottleneck. I've seen reports that were perfectly fine with DirectQuery suddenly to a loading failure when the data grew or more users are using it.

So for me, it comes down to:

• Direct Lake = more engineering work upfront, but better performance and scalability
• DirectQuery = faster to set up, but can hit performance walls if your queries get complex

Both have their place. I use DirectQuery for quick simple and operational dashboards, but for enterprise reporting with lots of users, the Direct Lake approach (with a good Gold-layer star schema) has been more reliable with precalculated columns.