Lag issue when using assetbundles

Game works fine without any lag at 30fps when i create build without assetbundle.
As i want my executable to be of less size, i chose to use assetbundle.
I have created assetbudle of game data (mainly created assetbundle of all prefabs with complete dependencies)and
read it through script and assigned it to respective objects.
But now game runs at 20FPS.
have i done anything wrong? please help me through this.
Thanks in advance.

Assetbundles are loaded on demand, dinamically. Without assetbundles you get all the data for the game in small, separate, pieces, but a lot of that data is duplicated. Assetbundles strip down the duplicated data, but the downside is that they are loaded in big chunks, so you get that lag.

In the end you have to decide: smaller exe, with a bit of lag, or larger exe with low lag. There might also be some way to optimize assetbundle loading, but I’ve found none.