Search slower with WPML | WordPress.org

Hi just want to let you know, great plugin, and I’m using this plugin this plugin without problem on 1500+ posts with inverted index.

But the problem started when we use wpml & translated into 5 languages (yes I know it’s a lot). The search become slower, maybe because the efficiency of the inverted index with multi lingual? Do the plugin also search posts and contents from other languages when user search with original language? How does it really works with multi language content?

Is there anything I can do to make the search faster? I have increase memory limit into 8gb for wp memory limit (we’re on vps 4vcpu and 16gb memory)

Thanks in advance