This document provides an overview of system design interviews. It discusses that the interviews focus on designing large-scale systems with open-ended questions in 30-40 minutes focusing on high-level architecture. Companies are looking at an applicant's ability to analyze complex problems, build large systems, and communicate effectively. The document provides tips for the interview and a step-by-step guide to the design process covering requirements, estimation, interfaces, data modeling, and more. It also discusses common design topics like caching, sharding, and databases and how to effectively answer questions regarding use cases, constraints, APIs, and other technical components of a system design.

1. System Design Interview
Mariia Danilenko
May 2018

2. What are system
design interviews?
Main characteristics of interviews:
● questions are open-ended
● 30 to 40 minutes to answer questions
● high-level architecture
Companies are looking at:
● ability to analyze complicated problem
● compatibility with building large systems
● communication skills

3. Interview tips
● Spend a few minutes questioning the
interviewer to comprehend the full scope of the
system
● Never assume things that are not explicitly
stated
● Lead the conversation
● Solve by breaking down
● Understand what your interviewer intends to
focus on
● Talk about trade-offs (!!!!!!!)
● Write key values

4. A step by step guide
Step 1: Requirements clarifications
Step 2: System interface definition
Step 3: Back-of-the-envelope estimation
Step 4: Defining data model
Step 5: High-level design
Step 6: Detailed design
Step 7: Identifying and resolving bottlenecks

5. Main topics
● Load Balancing
● Caching
○ Distributed cache
○ Global Cache
● Sharding or Data Partitioning
○ Methods
■ Horizontal partitioning
■ Vertical Partitioning
○ Partitioning Criteria
■ Key or Hash-based partitioning:
■ List partitioning
■ Round-robin partitioning
■ Composite partitioning
● Indexes
● Redundancy and Replication
● SQL vs NoSQL
● CAP Theorem
● Consistent Hashing

6. How to answer?
● Business use case
● Requirements:
○ Functional
○ Non-Functional
○ Extended
● Capacity Estimation and Constraints
○ Quantity of Reads vs Quantity of Writes
○ Storage estimates
■ Each object * size + think about retention
○ Bandwidth estimates
○ Memory estimates (cache %)
● System APIs
● Database Design
○ Database Schema
○ What kind of database should we use?
● Algorithm
● Data Partitioning and Replication
● Cache
○ How much cache should we have?
○ Eviction policy
● DB cleanup
● Load Balancer (LB)
● Security and Permissions

7. How to prepare?
Go through all examples in the book
Grokking the SD interview
Yelp's pipeline
Netflix's pipeline
AirBnB’s pipeline
Facebook's Presto
Pinterest
Twitter's blog
Uber's engineering blog