System Design

Learn System Design

How to Learn System Design?

Functional vs. Non-functional Requirements

What are Back-of-the-Envelope Estimations?

Things to Avoid During System Design Interview

System Design Basics

Load Balancing

Introduction to Load Balancing

Load Balancing Algorithms

Uses of Load Balancing

Load Balancer Types

Stateless vs. Stateful Load Balancing

High Availability and Fault Tolerance

Scalability and Performance

Challenges of Load Balancers

Introduction to API Gateway

Usage of API gateway

Advantages and disadvantages of using API gateway

Scalability

Availability

Latency and Performance

Concurrency and Coordination

Monitoring and Observability

Resilience and Error Handling

Fault Tolerance vs. High Availability

HTTP vs. HTTPS

TCP vs. UDP

HTTP: 1.0 vs. 1.1 vs 2.0 vs. 3.0

URL vs. URI vs. URN

Introduction to DNS

DNS Resolution Process

DNS Load Balancing and High Availability

Introduction to Caching

Why is Caching Important?

Types of Caching

Cache Replacement Policies

Cache Invalidation

Cache Read Strategies

Cache Coherence and Consistency Models

Caching Challenges

Cache Performance Metrics

What is CDN?

Origin Server vs. Edge Server

CDN Architecture

Push CDN vs. Pull CDN

Introduction to Data Partitioning

Partitioning Methods

Data Sharding Techniques

Benefits of Data Partitioning

Common Problems Associated with Data Partitioning

What is a Proxy Server?

Uses of Proxies

VPN vs. Proxy Server

What is Redundancy?

What is Replication?

Replication Methods

Data Backup vs. Disaster Recovery

Introduction to CAP Theorem

Components of CAP Theorem

Trade-offs in CAP Theorem

Examples of CAP Theorem in Practice

Beyond CAP Theorem

System Design Trade-offs in Interviews

Introduction to Databases

SQL Databases

NoSQL Databases

SQL vs. NoSQL

ACID vs BASE Properties

Real-World Examples and Case Studies

SQL Normalization and Denormalization

In-Memory Database vs. On-Disk Database

Data Replication vs. Data Mirroring

Database Federation

What are Indexes?

Types of Indexes

Introduction to Bloom Filters

Benefits & Limitations of Bloom Filters

Variants and Extensions of Bloom Filters

Applications of Bloom Filters

Difference Between Long-Polling, WebSockets, and Server-Sent Events

Why Quorum?

What is Quorum?

What is Heartbeat?

What is Checksum?

Uses of Checksum

What is Leader and Follower Pattern?

What is Security and Privacy?

What is Authentication?

What is Authorization?

Authentication vs. Authorization

OAuth vs. JWT for Authentication

What is Encryption?

What are DDoS Attacks?

Introduction to Messaging System

Introduction to Kafka

Messaging patterns

Popular Messaging Queue Systems

RabbitMQ vs. Kafka vs. ActiveMQ

Scalability and Performance

What is a Distributed File System?

Architecture of a Distributed File System

Key Components of a DFS

Batch Processing vs. Stream Processing

XML vs. JSON

Synchronous vs. Asynchronous Communication

Push vs. Pull Notification Systems

Microservices vs. Serverless Architecture

Message Queues vs. Service Bus

Stateful vs. Stateless Architecture

Event-Driven vs. Polling Architecture

Quiz

Importance of Discussing Trade-offs

Strong vs Eventual Consistency

Latency vs Throughput

ACID vs BASE Properties in Databases

Read-Through vs Write-Through Cache

Batch Processing vs Stream Processing

Load Balancer vs. API Gateway

API Gateway vs Direct Service Exposure

Proxy vs. Reverse Proxy

API Gateway vs. Reverse Proxy

SQL vs. NoSQL

Primary-Replica vs Peer-to-Peer Replication

Data Compression vs Data Deduplication

Server-Side Caching vs Client-Side Caching

REST vs RPC

Polling vs. Long-Polling vs. WebSockets vs. Webhooks

CDN Usage vs Direct Server Serving

Serverless Architecture vs Traditional Server-based

Stateful vs Stateless Architecture

Hybrid Cloud Storage vs All-Cloud Storage

Token Bucket vs Leaky Bucket

Read Heavy vs Write Heavy System

Quiz

System Design Interviews - A step by step guide

System Design Master Template

Designing a URL Shortening Service like TinyURL

Quiz - Designing URL Shortner

Designing Pastebin

Quiz - Designing Pastebin

Designing Instagram

Quiz - Designing Instagram

Designing Dropbox

Quiz - Designing Dropbox

Designing Facebook Messenger

Quiz - Designing Facebook Messenger

Designing Twitter

Quiz - Designing Twitter

Designing Youtube or Netflix

Quiz - Designing Youtube

Designing Typeahead Suggestion

Quiz - Designing Typeahead Suggestion

Designing an API Rate Limiter

Quiz - Designing an API Rate Limiter

Designing Twitter Search

Quiz - Designing Twitter Search

Designing a Web Crawler

Quiz - Designing a Web Crawler

Designing Facebook’s Newsfeed

Quiz - Designing Facebook’s Newsfeed

Designing Yelp or Nearby Friends

Quiz - Designing Yelp or Nearby Friends

Designing Uber backend

Quiz - Designing Uber backend

Designing Ticketmaster

Quiz - Designing Ticketmaster

Dynamo: Introduction

High-Level Architecture

Data Partitioning

Replication

Vector Clocks and Conflicting Data

The Life of Dynamo’s put() & get() Operations

Anti-entropy Through Merkle Trees

Gossip Protocol

Dynamo Characteristics and Criticism

Summary: Dynamo

Quiz: Dynamo

Mock Interview: Dynamo

YouTube Likes Counter

Quiz

Cassandra: Introduction

High-level Architecture

Replication

Cassandra Consistency Levels

Gossiper

Anatomy of Cassandra's Write Operation

Anatomy of Cassandra's Read Operation

Compaction

Tombstones

Summary: Cassandra

Quiz: Cassandra

Mock Interview: Cassandra

Messaging Systems: Introduction

Kafka: Introduction

High-level Architecture

Kafka: Deep Dive

Consumer Groups

Kafka Workflow

Role of ZooKeeper

Controller Broker

Kafka Delivery Semantics

Kafka Characteristics

Summary: Kafka

Quiz: Kafka

Mock Interview: Kafka

Chubby: Introduction

High-level Architecture

Design Rationale

How Chubby Works

File, Directories, and Handles

Locks, Sequencers, and Lock-delays

Sessions and Events

Master Election and Chubby Events

Caching

Database

Scaling Chubby

Summary: Chubby

Quiz: Chubby

Mock Interview: Chubby

Hadoop Distributed File System: Introduction

High-level Architecture

Deep Dive

Anatomy of a Read Operation

Anatomy of a Write Operation

Data Integrity & Caching

Fault Tolerance

HDFS High Availability (HA)

HDFS Characteristics

Summary: HDFS

Quiz: HDFS

Mock Interview: HDFS

Google File System: Introduction

High-level Architecture

Single Master and Large Chunk Size

Metadata

Master Operations

Anatomy of a Read Operation

Anatomy of a Write Operation

Anatomy of an Append Operation

GFS Consistency Model and Snapshotting

Fault Tolerance, High Availability, and Data Integrity

Garbage Collection

Criticism on GFS

Summary: GFS

Quiz: GFS

Mock Interview: GFS

BigTable: Introduction

BigTable Data Model

System APIs

Partitioning and High-level Architecture

SSTable

GFS and Chubby

Bigtable Components

Working with Tablets

The Life of BigTable's Read & Write Operations

Fault Tolerance and Compaction

BigTable Refinements

BigTable Characteristics

Summary: BigTable

Quiz: BigTable

Mock Interview: BigTable

Design Reddit

Quiz

Designing a Notification System

Quiz

Design Google calendar (Medium)

Quiz

Design a Recommendation System for Netflix

Quiz

Design Gmail

Quiz

Design Google News, a Global News Aggregator System (Medium)

Quiz

Design Unique ID Generator (Easy)

Quiz

Design Code Judging System like LeetCode (Medium)

Quiz

Design Payment System

Quiz

Design a Flash Sale for an E-commerce Site (Hard)

Quiz

Design a Reminder Alert System

Quiz

Introduction: System Design Patterns

1. Bloom Filters

2. Consistent Hashing

3. Quorum

4. Leader and Follower

5. Write-ahead Log

6. Segmented Log

7. High-Water Mark

8. Lease

9. Heartbeat

10. Gossip Protocol

11. Phi Accrual Failure Detection

12. Split Brain

13. Fencing

14. Checksum

15. Vector Clocks

16. CAP Theorem

17. PACELC Theorem

18. Hinted Handoff

19. Read Repair

20. Merkle Trees

Quiz

Challenges of Load Balancers

Challenges of Load Balancers

load balancing

high availability

fault tolerance

latency

+3

hard
·
5 min
·Updated Jan 2025

Load balancers play a crucial role in distributing traffic and optimizing resource utilization in modern applications. However, they are not without potential challenges or problems. Some common issues associated with load balancers include:

1. Single Point of Failure

If not designed with redundancy and fault tolerance in mind, a load balancer can become a single point of failure in the system. If the load balancer experiences an outage, it could impact the entire application.

  • Remedy: Implement high availability and failover mechanisms, such as redundant load balancer instances, to ensure continuity even if one instance fails.

2. Configuration Complexity

Load balancers often come with a wide range of configuration options, including algorithms, timeouts, and health checks. Misconfigurations can lead to poor performance, uneven traffic distribution, or even service outages.

  • Remedy: Regularly review and update configurations, and consider using automated configuration tools or expert consultation to ensure optimal settings.

3. Scalability Limitations

As traffic increases, the load balancer itself might become a performance bottleneck, especially if it is not configured to scale horizontally or vertically.

  • Remedy: Plan for horizontal or vertical scaling of the load balancer to match traffic demands, and use scalable cloud-based load balancing solutions.

4. Latency

Introducing a load balancer into the request-response path adds an additional network hop, which could lead to increased latency. While the impact is typically minimal, it is essential to consider the potential latency introduced by the load balancer and optimize its performance accordingly.

  • Remedy: Optimize load balancer performance through efficient routing algorithms and by placing the load balancer geographically close to the majority of users.

5. Sticky Sessions

Some applications rely on maintaining session state or user context between requests. In such cases, load balancers must be configured to use session persistence or "sticky sessions" to ensure subsequent requests from the same user are directed to the same backend server. However, this can lead to uneven load distribution and negate some of the benefits of load balancing.

  • Remedy: Employ advanced load balancing techniques that balance the need for session persistence with even traffic distribution, or redesign the application to reduce dependence on session state.

6. Cost

Deploying and managing load balancers, especially in high-traffic scenarios, can add to the overall cost of your infrastructure. This may include hardware or software licensing costs, as well as fees associated with managed load balancing services provided by cloud providers.

  • Remedy: Opt for cost-effective load balancing solutions, such as open-source software or cloud-based services that offer pay-as-you-go pricing models.

7. Health Checks and Monitoring

Implementing effective health checks for backend servers is essential to ensure that the load balancer accurately directs traffic to healthy instances. Misconfigured or insufficient health checks can lead to the load balancer sending traffic to failed or underperforming servers, resulting in a poor user experience.

  • Remedy: Implement comprehensive and regular health checks for backend servers, and use real-time monitoring tools to ensure traffic is always directed to healthy instances.

Despite these potential challenges, load balancers are an essential component of modern applications and can significantly improve performance, fault tolerance, and resource utilization when configured and managed correctly.

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