I worked once in a company which had this tourist app which should show places on map of the city. Unfortunately it slowed the App down to load more then a couple of places. Their solution was to limit the number of loaded places to teb and prohibited zomming out. I made it handle thousands of places at the same time. Main reason for the Performance issue was, that they sent all data they had about places big, big json objects with large text blobs) to the frontend. This part was easy, I instead sent only the data needed for the map like coordinates and icon type obviously. But still the backend struggeled hard with many objects from the DB, because they built a really shitty orm or what ever this was supposed to be: every line of data retrieved from the DB was immideatly wrapped in some class wich direved from another class which had some magic methods in it which caused some absurd loops over all other obejcts and even more DB queries in unexpected moments and also in the fucking constructor. So it turrned out that the map issue was only the top of the iceberg, since using any data from the DB was extremely expensive. The hard part was to understand the insaness of this abnormination and find the bottlenecks.