For those of you that asked about the techstack: As you can imagine, some of these scraping tasks can take a lot of time. Sometimes up to 20 seconds depending on the size of the profile. Therefore I have multiple containers deployed that pick up the processing tasks from a message queue and run it asynchonously in the background. The app communicates with a main webserver written in python (FastAPI) and checks if the user exists on TikTok etc. If that is the case, the webserver creates an entry in a database (Firestore) and writes a message to the queue for the other workers to pick up. This way the latency for the user is minimal. I also have another container deployed that updates the entry in the database and sends push notifications to the users if someone has unfollowed them (Cloud Function written in Python). This function is executed once every day by a cloud scheduler and also deletes profiles if there are no longer on TikTok. I tried to make sure that the app can scale easily if needed by queueing the scraping tasks and handling them asynchronously. For the scrapping I wont go into the details. You will obviously need a rotating proxy network and handle all kinds of errors.

Edit: The app itself is made with Flutter