Finding users node based on longitude and latitude

  1. What details are stored in each node of quad tree?
  2. When user logs in to system, we will only have user’s longitude and latitude. How will we find the associated node in quadtree for user? At every node, we have 4 choices(Children), we cannot scan all the nodes as it will be time consuming O(N)
  3. The course mentions 2 things
  • grid (store data in database : lat, long, gridid) along with cache
  • quad tree creation and usage
    These 2 are two different approaches or all of them are part of single approach?

Course: Grokking the System Design Interview - Learn Interactively
Lesson: Designing Twitter - Grokking the System Design Interview