How can I ensure high performance

Use previewing documents is a matter of retrieving a small graphical pre-generated image. This is done at high speed with a very little workload.

The file previews are pre-generated and cached by the Search & Preview Conversion servers.
Search & Preview Preview does not rely on OWA servers and do not need resources for generating previews as people access documents.

During the initial implementation of Search & Preview Preview, all file previews are not available until the initial conversion process has completed.

However, you can configure document libraries less frequently accessed to use the on-demand conversion process which is similar in architecture as the OWA except it supports +500 file formats and is significantly faster.