Making a payment system (using a 3rd party PSP):

• More focus on high level > low level data structures

Search engines

• low level understanding of data structures + systems

Define the Goal:

• Non technical requirements
• Given hypothesis / limitations of the problem

Functional Requirements:

• Technical requirements (Capacity, Read, Writes, etc)

Capacity Estimation:

• Take the biggest problem and find capacity needed for that, can be:

  • Read Complexity -> worst case TC / Payload size
  • Write complexity -> worst case TC / Cache size
  • other like max bandwidth, worse case latency, etc..

• Usually depends on type of problem (from functional requirements)

• A good shortcut for capacity (size) approximation:

Approaches

1. Usually addressing the problems, and solving one by one, example:
   • Data structures to be used for read / write?
   • Processing: Stream / Batch?
   • Connections? REST / GraphQL / RPC?
2. low level estimation, iterate over and over again.

System Components

• After solving problems, make system depending on that
  • System Design (Diagram)
  • Components Breakdown (optional - adding context)
• Simpler as possible -> think of scale as well, but main focus is solving the problem in hand.

Summary / Solution

• Overall, if multiple approaches are give, providing final suggestion
• Suggestion for scale / ways to improve, etc.