Well, Very interesting topic and few have faced this issue in their day to day typing habits.
Lets go to do something helpful for you, It may on Google or somewhere but whatever we are suggesting you, may or may not help you.
Scene: Whenever you type anything while using WhatsApp, your keyboard is lagging. It takes time or forget the typing rhythm. Well our fingers has got some motions while pressing keyboards. aha..
When you are on iPhone, it is very easy to find solution on google. Go to iPhone Settings > General > Reset > Reset Keyboard Dictionary.
When you are on Android, have you googled it ? Not yet..
Lets do some small efforts from our-side, it is not exact what you are looking for but trust us that, it helps me for my Android Phone. And what is that ?
Every Application creates Cache Memory in background. We need to clear that Cache.
Go to App Info > Storage > Clear Cache
once you clear the cache, go to you WhatsApp and try your keyboard. It helps better for me. And Yes whatever method on Google – If it helps you then go ahead with that. everyone has different problem with their Phones. Let us know what is yours ?
Happy Typing !