Searching is one of the most important features of any mobile application that deals with data. It is almost inevitable to not have a reliable and consistent search in a mobile application these days. If your app deals with data that it retrieves from an API or a web service, you can have the backend developers develop the search mechanism for you and you can then consume the search results via the API, but, if you are using something like Cloud Firestore to store your data, you are in a puddle.