System design interview structure in HLD - Architecture Diagram

System Overview - System design interview structure

This system organizes and manages the flow of a system design interview. It ensures smooth communication between the interviewer and candidate, tracks questions, and records answers. The system supports scheduling, live interaction, and feedback collection.

Architecture Diagram

User(Client)  
    |       
    v       
Load Balancer
    |       
    v       
API Gateway
    |       
    v       
Interview Service <-> Question DB
    |       
    v       
Feedback Service
    |
    v
Notification Service

Components

User(Client)

client

Person participating in the interview, either interviewer or candidate

Load Balancer

load_balancer

Distributes incoming requests evenly to backend services

API Gateway

api_gateway

Routes requests to appropriate services and handles authentication

Interview Service

service

Manages interview sessions, question flow, and live interaction

Question DB

database

Stores system design questions and related metadata

Feedback Service

service

Collects and stores feedback from interviewer and candidate

Notification Service

service

Sends notifications and reminders about interview schedules and updates

Request Flow - 9 Hops

User(Client) → Load Balancer

Load Balancer → API Gateway

API Gateway → Interview Service

Interview Service → Question DB

Interview Service → User(Client)

User(Client) → Interview Service

Interview Service → Feedback Service

Feedback Service → Notification Service

Notification Service → User(Client)

Failure Scenario

Component Fails:Interview Service

Impact:Interview sessions cannot be managed, questions not delivered, answers not recorded

Mitigation:Use service replication and failover to backup instances; queue requests temporarily

Architecture Quiz - 3 Questions

Which component routes user requests to the correct backend service?

A Interview Service

B Load Balancer

C API Gateway

D Notification Service

Design Principle

This architecture demonstrates separation of concerns by dividing responsibilities into specialized services. It uses a load balancer and API gateway to manage traffic and routing, ensuring scalability and security. Data storage is separated for questions and feedback, enabling focused optimization and reliability.

Practice

1. What is the first step you should take when starting a system design interview?

easy

A. Discuss the deployment strategy

B. Start coding the solution immediately

C. Draw the final architecture diagram

D. Understand the problem requirements clearly

Solution

1. Step 1: Identify the initial focus in system design

   The first step is to understand the problem requirements clearly to know what needs to be built.

2. Step 2: Avoid premature actions

   Jumping to coding or drawing diagrams without understanding leads to wasted effort and confusion.

3. Final Answer:

   Understand the problem requirements clearly -> Option D

4. Quick Check:

   First step = Understand requirements [OK]

Hint: Always clarify requirements before designing [OK]

Common Mistakes:

• Starting design without clarifying requirements
• Jumping to coding too early
• Ignoring problem constraints

2. Which of the following is the correct order of steps in a typical system design interview?

easy

A. Design components -> Write code -> Understand requirements -> Define APIs

B. Understand requirements -> Define APIs -> Design components -> Discuss trade-offs

C. Write code -> Define APIs -> Understand requirements -> Discuss trade-offs

D. Discuss trade-offs -> Write code -> Design components -> Understand requirements

Solution

1. Step 1: Recall the logical flow of system design

   The correct flow starts with understanding requirements, then defining APIs, designing components, and finally discussing trade-offs.

2. Step 2: Eliminate incorrect sequences

   Writing code is usually not part of the initial design steps, so options with coding first are incorrect.

3. Final Answer:

   Understand requirements -> Define APIs -> Design components -> Discuss trade-offs -> Option B

4. Quick Check:

   Logical design flow = Understand requirements -> Define APIs -> Design components -> Discuss trade-offs [OK]

Hint: Follow problem -> APIs -> design -> trade-offs order [OK]

Common Mistakes:

• Starting with coding instead of design
• Skipping API definition
• Discussing trade-offs too early

3. During a system design interview, you propose a caching layer to improve performance. Which of the following is the most likely benefit you should mention?

medium

A. Increases database storage capacity

B. Eliminates the need for load balancers

C. Reduces database load and decreases response time

D. Automatically scales the number of servers

Solution

1. Step 1: Understand caching purpose in system design

   Caching stores frequently accessed data closer to the user, reducing database queries and improving response time.

2. Step 2: Evaluate other options

   Increasing storage, removing load balancers, or auto-scaling servers are unrelated to caching benefits.

3. Final Answer:

   Reduces database load and decreases response time -> Option C

4. Quick Check:

   Caching benefit = Reduced load and latency [OK]

Hint: Cache reduces DB hits and speeds up responses [OK]

Common Mistakes:

• Confusing caching with storage increase
• Thinking caching replaces load balancers
• Assuming caching auto-scales servers

4. You designed a system with a single database server. During the interview, the interviewer points out a potential bottleneck. What is the most likely issue?

medium

A. Single point of failure and limited scalability

B. Too many load balancers causing delays

C. Excessive caching leading to stale data

D. Overuse of microservices causing complexity

Solution

1. Step 1: Analyze single database server drawbacks

   A single database server can fail and cannot handle very high traffic, causing bottlenecks.

2. Step 2: Check other options for relevance

   Load balancers, caching, and microservices issues are unrelated to having a single DB server.

3. Final Answer:

   Single point of failure and limited scalability -> Option A

4. Quick Check:

   Single DB = bottleneck and failure risk [OK]

Hint: Single DB risks failure and limits scale [OK]

Common Mistakes:

• Blaming load balancers for DB bottleneck
• Confusing caching issues with DB limits
• Ignoring single point of failure risk

5. In a system design interview, after presenting your architecture, the interviewer asks you to handle sudden traffic spikes. Which approach best addresses this?

hard

A. Implement auto-scaling with load balancers to add/remove servers dynamically

B. Use a single powerful server to handle all traffic

C. Remove caching to reduce complexity

D. Store all data in a single database to simplify writes

Solution

1. Step 1: Understand traffic spike handling

   Auto-scaling with load balancers allows the system to add or remove servers based on traffic, handling spikes efficiently.

2. Step 2: Evaluate other options

   A single server cannot handle spikes well; removing caching or using one DB limits performance and scalability.

3. Final Answer:

   Implement auto-scaling with load balancers to add/remove servers dynamically -> Option A

4. Quick Check:

   Traffic spikes = Auto-scaling + load balancers [OK]

Hint: Use auto-scaling and load balancers for spikes [OK]

Common Mistakes:

• Relying on one server for high traffic
• Removing caching unnecessarily
• Ignoring scalability needs