Alex Xu
@alexxubyte
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Co-Founder of ByteByteGo | Author of the bestselling book series: ‘System Design Interview’ | YouTube:
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The Big Archive for System Design - 2023 Edition (PDF) is available now. And it's completely FREE.
The PDF contains 𝐚𝐥𝐥 𝐦𝐲 𝐭𝐞𝐜𝐡𝐧𝐢𝐜𝐚𝐥 𝐩𝐨𝐬𝐭𝐬 published in 2023.
What’s included in the PDF?
🔹 Netflix's Tech Stack
🔹 Top 5 common ways to improve API
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/1 How do Apple Pay and Google Pay handle sensitive card info?
The diagram below shows the differences. Both approaches are very secure, but the implementations are different. To understand the difference, we break down the process into two flows.
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Twitter Architecture 2022 vs. 2012. What’s changed over the past 10 years?
Thank you,
@elonmusk
for the transparency.
{1/2}
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Explaining 8 Popular Network Protocols in 1 Diagram. The method to download the high-resolution PDF is available at the end.
Network protocols are standard methods of transferring data between two computers in a network.
1. HTTP (HyperText Transfer Protocol)
HTTP is a protocol
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/1 Why is the credit card called “𝐭𝐡𝐞 𝐦𝐨𝐬𝐭 𝐩𝐫𝐨𝐟𝐢𝐭𝐚𝐛𝐥𝐞 product in banks”? How does VISA/Mastercard make money?
The diagram below shows the economics of the credit card payment flow.
1. The cardholder pays a merchant $100 to buy a product.
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/1 Want to know the secret to optimizing your SQL queries? Understanding the execution order is key.
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1/ The Unified Payments Interface (UPI) for real-time transactions in India is a good case study for other nations in the payment space.
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/1 𝐖𝐡𝐚𝐭 𝐀𝐫𝐞 𝐭𝐡𝐞 𝐆𝐫𝐞𝐞𝐧𝐞𝐬𝐭 𝐏𝐫𝐨𝐠𝐫𝐚𝐦𝐦𝐢𝐧𝐠 𝐋𝐚𝐧𝐠𝐮𝐚𝐠𝐞𝐬 [1]?
The study below runs 10 benchmark problems in 28 languages. It measures the runtime, memory usage, and energy consumption of each language. The abstract of the paper is shown below.
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/1 Why is a credit card called a “𝐜𝐫𝐞𝐝𝐢𝐭” card?
Why is a debit card called a “𝐝𝐞𝐛𝐢𝐭” card?
An example of a debit card payment is shown in the diagram below. 👇
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How do companies ship code to production? The method to download the high-resolution PDF is available at the end.
The diagram below illustrates the typical workflow.
Step 1: The process starts with a product owner creating user stories based on requirements.
Step 2: The dev
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Really cool neovim plugin. I hope everyone takes a break from coding and has a great weekend.
Github repo:
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My recommended materials for cracking your next technical interview:
Coding
- Leetcode
- Cracking the coding interview book
- Neetcode
System Design Interview
- System Design Interview book 1, 2 by Alex Xu
- Grokking the system design by Design Guru
- Design Data-intensive
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/1 How will you design the Stack Overflow website? If your answer is on-premise servers and monolith (bottom), you would likely fail the interview, but that's how it is built in reality!
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Would it be nice if the code we wrote automatically turned into architecture diagrams?
I recently discovered a Github repo that does exactly this: Diagram as Code for prototyping cloud system architectures.
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Explaining JSON Web Token (JWT) to a 10 year old Kid.
Imagine you have a special box called a JWT. Inside this box, there are three parts: a header, a payload, and a signature.
The header is like the label on the outside of the box. It tells us what type of box it is and how
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How does VISA work when we 𝐬𝐰𝐢𝐩𝐞 𝐚 𝐜𝐫𝐞𝐝𝐢𝐭 𝐜𝐚𝐫𝐝 at a merchant’s shop?
VISA, Mastercard, and American Express act as card networks for the clearing and settling of funds. The card acquiring bank and the card issuing bank can be – and often are – different.
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Explaining JSON Web Token (JWT) to a 10 year old Kid.
Imagine you have a special box called a JWT. Inside this box, there are three parts: a header, a payload, and a signature.
The header is like the label on the outside of the box. It tells us what type of box it is and how
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How do you pay from your digital wallets, such as Paytm, Paypal, and Venmo, by scanning the QR code?
To understand the process involved, we need to divide the “scan to pay” process into two sub-processes:
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1/10 Session, cookie, JWT, token, SSO, and OAuth 2.0 - what are they?
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OAuth 2.0 Explained With Simple Terms.
OAuth 2.0 is a powerful and secure framework that allows different applications to securely interact with each other on behalf of users without sharing sensitive credentials.
The entities involved in OAuth are the User, the Server, and
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/1 8 Data Structures That Power Your Databases. Which one should we pick?
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GET, POST, PUT, DELETE… A list of common HTTP “verbs” in one diagram. The method to download the high-resolution PDF is available at the end.
1. HTTP GET
This retrieves a resource from the server. It is idempotent. Multiple identical requests return the same result.
2. HTTP
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What are some of the algorithms we should know before taking system design interviews?
I put together a list and explained why they are important.
To learn more:
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Linux file system explained.
The Linux file system used to resemble an unorganized town where individuals constructed their houses wherever they pleased. However, in 1994, the Filesystem Hierarchy Standard (FHS) was introduced to bring order to the Linux file system.
By
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Popular interview question: how to diagnose a mysterious process that’s taking too much CPU, memory, IO, etc?
The diagram below illustrates helpful tools in a Linux system.
🔹‘vmstat’ - reports information about processes, memory, paging, block IO, traps, and CPU activity.
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Unit tests vs. Staging vs. Production
Production will always humble your code, so be well prepared.
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/1 What does API gateway do?
The diagram below shows the detail.
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What happens when you type a URL into a browser? The method to download the high-resolution PDF is available at the end.
Let’s look at the process step by step.
Step 1: The user enters a URL (bytebytego .com) into the browser and hits Enter. The first thing we need to do is to
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/1 Why is Nginx called a “𝐫𝐞𝐯𝐞𝐫𝐬𝐞” proxy?
The diagram below shows the differences between a 𝐟𝐨𝐫𝐰𝐚𝐫𝐝 𝐩𝐫𝐨𝐱𝐲 and a 𝐫𝐞𝐯𝐞𝐫𝐬𝐞 𝐩𝐫𝐨𝐱𝐲.
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CI/CD Pipeline Explained to Kids
Section 1 - SDLC with CI/CD
The software development life cycle (SDLC) consists of several key stages: development, testing, deployment, and maintenance. CI/CD automates and integrates these stages to enable faster, more reliable releases.
When
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Popular interview question: what’s the difference between Inner, Left, Right, and Full join?
The diagram below illustrates how different types of joins work.
(INNER) JOIN: returns only matching rows between both tables.
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How does Docker Work? Is Docker still relevant?
We just made a video on this topic.
Docker's architecture comprises three main components:
🔹 Docker Client
This is the interface through which users interact. It communicates with the Docker daemon.
🔹 Docker Host
Here, the
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Twitter has enforced very strict rate limiting. Some people cannot even see their own tweets.
Rate limiting is a very important yet often overlooked topic. Let's use this opportunity to take a look at what it is and the most popular algorithms.
A thread.
#RateLimitExceeded
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/1 I’ve been writing the system design newsletter for 6 months. Here are the 5 most popular ones: 👇
Link:
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Top 4 Forms of Authentication Mechanisms
1. SSH Keys:
Cryptographic keys are used to access remote systems and servers securely
2. OAuth Tokens:
Tokens that provide limited access to user data on third-party applications
3. SSL Certificates:
Digital certificates ensure secure
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Netflix's Overall Architecture.
This post is based on research from many Netflix engineering blogs and open-source projects. If you come across any inaccuracies, please feel free to inform us.
Mobile and web: Netflix has adopted Swift and Kotlin to build native mobile apps. For
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Netflix's Tech Stack.
This post is based on research from many Netflix engineering blogs and open-source projects. If you come across any inaccuracies, please feel free to inform us.
Mobile and web: Netflix has adopted Swift and Kotlin to build native mobile apps. For its web
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Really cool and cute way to explain git commands.
By
@girlie_mac
If you like this kind of tech doodles, check out her Github repo:
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This is the flowchart of how slack decides to send a notification.
It is an excellent example of why a simple feature may take much longer.
This might also explain why people don’t get notifications or clear the red dots sometimes.
Img source: slack eng blog
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Top architectural styles
In software development, architecture plays a crucial role in shaping the structure and behavior of software systems. It provides a blueprint for system design, detailing how components interact with each other to deliver specific functionality. They
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/1 Evolution of Uber’s API layer
Uber’s API gateway went through 3 main stages.
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How does 𝐆𝐨𝐨𝐠𝐥𝐞 𝐀𝐮𝐭𝐡𝐞𝐧𝐭𝐢𝐜𝐚𝐭𝐨𝐫 (or other types of 2-factor authenticators) work?
Google authenticator is commonly used for logging into our accounts when 2-factor authentication is enabled. How does it guarantee security?
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/1 How does Git Work?
The diagram below shows the Git workflow.
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/1 How Discord Stores Trillions Of Messages
The diagram below shows the evolution of message storage at Discord:
MongoDB ➡️ Cassandar ➡️ ScyllaDB
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/1 Netflix Tech Stack - Part 1 (CI/CD Pipeline)
Planing: Netflix Engineering uses JIRA for planning and Confluence for documentation.
Coding: Java is the primary programming language for the backend service, while other languages are used for different use cases.
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HTTPS, SSL Handshake, and Data Encryption Explained to Kids.
HTTPS: Safeguards your data from eavesdroppers and breaches. Understand how encryption and digital certificates create an impregnable shield.
SSL Handshake: Behind the Scenes — Witness the cryptographic protocols that
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/1 Almost every software engineer has used Git before, but only a handful know how it works :) Let's dive in.
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IBM MQ -> RabbitMQ -> Kafka ->Pulsar, How do message queue architectures evolve?
🔹 IBM MQ
IBM MQ was launched in 1993. It was originally called MQSeries and was renamed WebSphere MQ in 2002. It was renamed to IBM MQ in 2014. IBM MQ is a very successful product widely used in
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Experience is the best teacher, particularly in times when we fail.
Great image by @ ferraroroberto on IG
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How do companies ship code to production?
The diagram below illustrates the typical workflow.
Step 1: The process starts with a product owner creating user stories based on requirements.
Step 2: The dev team picks up the user stories from the backlog and puts them into a
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How to store passwords safely in the database and how to validate a password? Let’s take a look.
𝐓𝐡𝐢𝐧𝐠𝐬 𝐍𝐎𝐓 𝐭𝐨 𝐝𝐨
🔹 Storing passwords in plain text is not a good idea because anyone with internal access can see them.
🔹 Storing password hashes directly is not
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Explaining 9 types of API testing. Next week's topic will be listed at the end.
🔹 Smoke Testing
This is done after API development is complete. Simply validate if the APIs are working and nothing breaks.
🔹 Functional Testing
This creates a test plan based on the functional
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Evolution of the Netflix API architecture.
The Netflix API architecture went through 4 main stages.
𝐌𝐨𝐧𝐨𝐥𝐢𝐭𝐡. The application is packaged and deployed as a monolith, such as a single Java WAR file, Rails app, etc. Most startups begin with a monolith architecture.
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/1 Can a web server provide real-time updates?
An HTTP server cannot automatically initiate a connection to a browser. As a result, the web browser is the initiator. What should we do next to get real-time updates from the HTTP server?
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/1 If you use JSON files, you'll probably like this tool 👇
Nested JSON files are hard to read.
𝐉𝐬𝐨𝐧𝐂𝐫𝐚𝐜𝐤 generates graph diagrams from JSON files and makes them easy to read.
Additionally, the generated diagrams can be downloaded as images.
See the link below.
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How does HTTPS work?
Hypertext Transfer Protocol Secure (HTTPS) is an extension of the Hypertext Transfer Protocol (HTTP.) HTTPS transmits encrypted data using Transport Layer Security (TLS.) If the data is hijacked online, all the hijacker gets is binary code.
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Explaining 9 types of API testing. The method to download the high-resolution PDF is available at the end.
🔹 Smoke Testing
This is done after API development is complete. Simply validate if the APIs are working and nothing breaks.
🔹 Functional Testing
This creates a test plan
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A visual guide on how to choose the right Database.
Picking a database is a long-term commitment so the decision shouldn’t be made lightly. The important thing to keep in mind is to choose the right database for the right job.
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Top 12 Tips for API Security
- Use HTTPS
- Use OAuth2
- Use WebAuthn
- Use Leveled API Keys
- Authorization
- Rate Limiting
- API Versioning
- Whitelisting
- Check OWASP API Security Risks
- Use API Gateway
- Error Handling
- Input Validation
--
Subscribe to our weekly
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URL, URI, URN - What are the differences?
The diagram below shows a comparison of URL, URI, and URN.
🔹 URI
URI stands for Uniform Resource Identifier. It identifies a logical or physical resource on the web. URL and URN are subtypes of URI. URL locates a resource, while URN
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1/2 Linux commands illustrated on one page!
🔹Controlling processes: kill, killall, nice
🔹Scheduliing jobs: sleep, watch, crontab
🔹Host location: host, whois, ping
🔹Many more
Subscribe to our weekly newsletter to learn something new every week:
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Linux file permission illustrated.
To understand Linux file permissions, we need to understand Ownership and Permission.
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/1 How do fintech startups find new opportunities among so many payment companies? What do PayPal, Stripe, and Square do exactly? 👇
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A nice cheat sheet of different cloud services.
--
Subscribe to our weekly newsletter to get a Free System Design PDF (158 pages):
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17 Equations That Changed the World. Happy Friday!
Subscribe to our weekly newsletter to learn something new every week:
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How Do C++, Java, Python Work?
The diagram shows how the compilation and execution work.
Compiled languages are compiled into machine code by the compiler. The machine code can later be executed directly by the CPU. Examples: C, C++, Go.
A bytecode language like Java, compiles
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I recently discovered a cheat sheet that covers many design patterns, intended to jog your memory about how different patterns work.
Page 1
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How is data sent over the network? Why do we need so many layers in the OSI model?
The diagram below shows how data is encapsulated and de-encapsulated when transmitting over the network.
1/9
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Which protocol does Zoom use for video streaming, TCP or UDP?
Let’s review the differences first.
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/1 How can Redis be used?
There is more to Redis than just caching.
Redis can be used in various scenarios, as shown in the diagram.
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1/ How do we design a 𝐜𝐡𝐚𝐭 𝐚𝐩𝐩𝐥𝐢𝐜𝐚𝐭𝐢𝐨𝐧 like WhatsApp, Facebook Messenger or Discord?
The diagram below shows a design for a simplified 1 to 1 chat application.
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My Favorite 10 Books for Software Developers
General Advice
1 - The Pragmatic Programmer by Andrew Hunt and David Thomas
2 - Code Complete by Steve McConnell: Often considered a bible for software developers, this comprehensive book covers all aspects of software development,
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How are notifications pushed to our phones or PCs?
A messaging solution (Firebase) can be used to support the notification push.
The diagram below shows how Firebase Cloud Messaging (FCM) works.
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How do we design a system using the 𝐞𝐯𝐞𝐧𝐭 𝐬𝐨𝐮𝐫𝐜𝐢𝐧𝐠 paradigm? How is it different from normal system design? What are the benefits? We will talk about it in this post.
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How does Twitter work? Let’s take a look at it from the architectural point of view before Elon takes it.
𝐓𝐡𝐞 𝐋𝐢𝐟𝐞 𝐨𝐟 𝐚 𝐓𝐰𝐞𝐞𝐭:
1️⃣ A tweet comes in through the Write API.
2️⃣ The Write API routes the request to the Fanout service.
#twitter
#systemdesign
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Git Merge vs. Rebase vs. Squash Commit!
What are the differences?
When we 𝐦𝐞𝐫𝐠𝐞 𝐜𝐡𝐚𝐧𝐠𝐞𝐬 from one Git branch to another, we can use ‘git merge’ or ‘git rebase’. The diagram below shows how the two commands work.
𝐆𝐢𝐭 𝐌𝐞𝐫𝐠𝐞
This creates a new commit G’
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/1 What does a typical microservice architecture look like? 👇
The diagram below shows a typical microservice architecture.
🔹Load Balancer: This distributes incoming traffic across multiple backend services.
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Top Architectural Styles.
The method to download the high-resolution image is available at the end.
In software development, architecture plays a crucial role in shaping the structure and behavior of software systems. It provides a blueprint for system design, detailing how
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Session, Cookie, JWT, Token, SSO, and OAuth 2.0 Explained in One Diagram
When you login to a website, your identity needs to be managed. Here is how different solutions work:
- Session - The server stores your identity and gives the browser a session ID cookie. This allows the
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The Evolving Landscape of API Protocols in 2023
This is a brief summary of the blog post I wrote for Postman.
In this blog post, I cover the six most popular API protocols: REST, Webhooks, GraphQL, SOAP, WebSocket, and gRPC. The discussion includes the benefits and challenges
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/1 How does 𝐠𝐑𝐏𝐂 work?
RPC (Remote Procedure Call) is called “𝐫𝐞𝐦𝐨𝐭𝐞” because it enables communications between remote services when services are deployed to different servers. From the user’s point of view, it acts like a local function call
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Diagram as code: 6 ways to turn code into beautiful architecture diagrams. A thread.
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Linux file system explained.
The Linux file system used to resemble an unorganized town where individuals constructed their houses wherever they pleased. However, in 1994, the Filesystem Hierarchy Standard (FHS) was introduced to bring order to the Linux file system.
By
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Top 12 Tips for API Security. Next week's topics will be listed at the end.
- Use HTTPS
- Use OAuth2
- Use WebAuthn
- Use Leveled API Keys
- Authorization
- Rate Limiting
- API Versioning
- Whitelisting
- Check OWASP API Security Risks
- Use API Gateway
- Error Handling
- Input
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Amazon Prime days are coming. Designing a system with extremely high concurrency, high availability, and quick responsiveness needs to consider many aspects 𝐚𝐥𝐥 𝐭𝐡𝐞 𝐰𝐚𝐲 𝐟𝐫𝐨𝐦 𝐟𝐫𝐨𝐧𝐭𝐞𝐧𝐝 𝐭𝐨 𝐛𝐚𝐜𝐤𝐞𝐧𝐝.
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System Design Blueprint: The Ultimate Guide.
Hope this checklist is useful to guide your discussions during the interview process.
This briefly touches on:
- LB
- Gateway
- Communication
- CDN
- Database
- Cache
- MQ
- ID Generation
- Scalability
- Availability
- More
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Docker 101: Streamlining App Deployment. The method to download the high-resolution PDF is available at the end.
Fed up with the "it works on my machine" dilemma? Docker could be your salvation!
Docker revolutionizes software development and deployment. Explore the essentials:
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What does API gateway do?
The diagram below shows the detail.
Step 1 - The client sends an HTTP request to the API gateway.
Step 2 - The API gateway parses and validates the attributes in the HTTP request.
Step 3 - The API gateway performs allow-list/deny-list checks.
Step 4
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System Design Blueprint: The Ultimate Guide.
The method to download the high-resolution PDF is available at the end.
We've created a template to tackle various system design problems in interviews.
Hope this checklist is useful to guide your discussions during the interview
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Next week, we will cover:
🔹 RPC - gRPC
🔹 RPC - Avro
🔹 Domain-driven design (DDD)
🔹 SQL optimization
🔹 API first design
Subscribe to our weekly newsletter to learn something new every week:
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/1 How does Docker work?
A comparison of Docker-based and non-Docker-based development is shown below.
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Almost every software engineer has used Git before, but only a handful know how it works.
To begin with, it's essential to identify where our code is stored. The common assumption is that there are only two locations - one on a remote server like Github and the other on our
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How does Netflix scale push messaging for millions of devices?
This post draws from an article published on Netflix’s engineering blog. Here’s my understanding of how the online streaming giant’s system works.
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Explaining 8 Popular Network Protocols in 1 Diagram.
You can find the link to watch a detailed video explanation at the end of the post.
Network protocols are standard methods of transferring data between two computers in a network.
1. HTTP (HyperText Transfer Protocol)
HTTP
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/1 What are the API architectural styles?
The diagram below shows the common API architectural styles in one picture:
1. REST
2. GraphQL
3. Web socket
4. Webhook
5. gRPC
6. SOAP
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/1 What are the common load-balancing algorithms?
The diagram below shows 6 common algorithms.
🔹 Static Algorithms
1. Round robin
The client requests are sent to different service instances in sequential order. The services are usually required to be stateless.
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/1 Why is PostgreSQL voted the 𝐦𝐨𝐬𝐭 𝐥𝐨𝐯𝐞𝐝 𝐝𝐚𝐭𝐚𝐛𝐚𝐬𝐞 by Stackoverflow 2022 Developer Survey?
The diagram shows the many use cases by PostgreSQL - one database that includes almost 𝐚𝐥𝐥 𝐭𝐡𝐞 𝐮𝐬𝐞 𝐜𝐚𝐬𝐞𝐬 developers need.
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