System design topics: start here
New to system design? First, you’ll need a basic understanding of common principles, learning about what they are, how they are used, and their pros and cons.Step 1: Review the scalability video lecture
Scalability Lecture at Harvard Topics covered:- Vertical scaling
- Horizontal scaling
- Caching
- Load balancing
- Database replication
- Database partitioning
Step 2: Review the scalability article
Scalability Topics covered:Next steps
Next, we’ll look at high-level trade-offs:- Performance vs scalability
- Latency vs throughput
- Availability vs consistency
Keep in mind that everything is a trade-off.
How to approach a system design interview question
The system design interview is an open-ended conversation. You are expected to lead it. You can use the following steps to guide the discussion. To help solidify this process, work through common system design interview questions using the following steps.Step 1: Outline use cases, constraints, and assumptions
Gather requirements and scope the problem. Ask questions to clarify use cases and constraints. Discuss assumptions.- Who is going to use it?
- How are they going to use it?
- How many users are there?
- What does the system do?
- What are the inputs and outputs of the system?
- How much data do we expect to handle?
- How many requests per second do we expect?
- What is the expected read to write ratio?
Step 2: Create a high level design
Outline a high level design with all important components.- Sketch the main components and connections
- Justify your ideas
Step 3: Design core components
Dive into details for each core component. For example, if you were asked to design a url shortening service, discuss:- Generating and storing a hash of the full url
- MD5 and Base62
- Hash collisions
- SQL or NoSQL
- Database schema
- Translating a hashed url to the full url
- Database lookup
- API and object-oriented design
Step 4: Scale the design
Identify and address bottlenecks, given the constraints. For example, do you need the following to address scalability issues?- Load balancer
- Horizontal scaling
- Caching
- Database sharding
Back-of-the-envelope calculations
You might be asked to do some estimates by hand. Refer to the following resources:- Use back of the envelope calculations
- Powers of two table
- Latency numbers every programmer should know