Networking

A 301 redirect says 'this page has PERMANENTLY moved to a new address.' Browsers remember it and go straight to the new URL next time.

A 302 redirect says 'this page is TEMPORARILY somewhere else — come back here later.' Browsers don't cache it and search engines don't transfer SEO juice.

An A Record is the most basic DNS record — it just says 'this domain name = this IP address.' It's the phonebook entry itself.

AMQP is the enterprise-grade messaging protocol behind RabbitMQ. It guarantees message delivery with routing, queuing, and acknowledgments.

An API Gateway is the front door for all your APIs.

Bandwidth is how wide your internet pipe is — how much data can flow through per second. A narrow pipe means slow speeds, a wide pipe means fast speeds.

Binary Protocols encode data as raw bytes instead of human-readable text.

Brotli is gzip's smarter cousin from Google. It compresses text files (HTML, CSS, JS) smaller than gzip, meaning pages load faster.

CIDR is the shorthand notation for specifying IP address ranges. '192.168.1.

A CNAME is a DNS record that's like an alias or nickname. Instead of pointing to an IP address directly, it points to another domain name. So 'www.

A circuit breaker monitors calls to a service and 'trips' when too many fail. Once tripped, it stops sending requests and fails fast instead of waiting for

Connection Pooling keeps a bucket of pre-opened database (or HTTP) connections ready to use. Instead of opening a new connection for every request (slow!

Connection reuse means keeping a TCP connection open after the first request so you can send more requests without the overhead of a new handshake each tim

Consistent Hashing distributes data across servers so that when you add or remove a server, only a small fraction of data needs to move. Normal hashing?

Content-Type is a header that tells the receiver what format the data is in. 'I'm sending you JSON.' 'I'm sending you a PNG image.' 'I'm sending you HTML.

A cookie is a tiny piece of data the server tells your browser to store and send back on every future request.

DHCP is the system that automatically assigns IP addresses to devices when they join a network.

DNS is the internet's phonebook. You type 'google.

DNS Round Robin is the simplest load balancing: one domain name, multiple IP addresses. DNS rotates through them for each request.

A domain name is the human-friendly name for a website, like 'google.com' instead of '142.250.80.46'.

A domain registrar is the shop where you buy domain names. Think Namecheap, GoDaddy, or Google Domains. You pay them yearly to 'own' your domain name.

Exponential backoff means waiting longer between each retry — 1 second, then 2, then 4, then 8. Instead of hammering a failing server every second, you giv

FTP is the old-school way to transfer files to a server. You connect with a username and password and upload or download files.

A firewall is the bouncer at your network's door. It checks every incoming and outgoing connection against a list of rules and blocks anything suspicious.

A forward proxy sits in front of clients (users), not servers. It sends requests on behalf of users so the destination can't see who's really asking.

HTTP is the language your browser uses to ask websites for stuff. You type a URL, your browser shouts 'hey, give me that page!

HTTP/2 is a supercharged version of HTTP. With HTTP/1.1, you could only ask for one thing at a time per connection.

HTTP/3 is the newest version of HTTP and it ditches TCP entirely in favor of QUIC.

HTTP/3 ditches TCP for QUIC (built on UDP), which means no more head-of-line blocking, faster connections, and built-in encryption.

HTTP/3 ditches TCP for QUIC, a protocol built on UDP that handles congestion, encryption, and multiplexing all at once. No more head-of-line blocking. No m

HTTPS is HTTP but with a bodyguard. All the data flying between your browser and the website is scrambled so nobody can spy on it.

Head-of-Line Blocking is when one slow request blocks everything behind it, like a slow car in a single-lane tunnel. In HTTP/1.

Headers are the metadata attached to HTTP requests and responses — information about the information.

Health Checks are the 'are you alive?' ping that load balancers send to your servers.

Health checks are like the doctor's checkup for your servers. The load balancer periodically asks 'are you alive? are you healthy?' and routes traffic only

IMAP is how your email client fetches email from the server.

IP is the postal system of the internet. Every device gets an address (an IP address) and all data gets wrapped in envelopes called packets.

An IP address is your device's home address on the internet.

IPv4 is the original address format for the internet — four numbers separated by dots, like 192.168.1.1. The problem?

IPv6 is the new, massive address format for the internet. Instead of four small numbers, it's eight groups of letters and numbers separated by colons.

Jitter adds randomness to your retry timing so all your clients don't retry at the exact same millisecond. Without jitter, exponential backoff creates sync

Keep-Alive tells the server 'don't hang up after this request — I've got more coming.

Latency is the delay before data starts moving — the time it takes for a request to go from your device to the server and back.

A load balancer is like a traffic cop for servers.

Load balancer algorithms decide which server gets the next request. Round robin takes turns. Least connections picks the least busy server. Weighted lets y

Long Polling is polling's smarter cousin. Instead of asking 'any updates?

A MIME type is a standardized label for what type of content something is. 'text/html' means HTML. 'image/jpeg' means a JPEG image.

MQTT is the WhatsApp of IoT devices. It's a super lightweight messaging protocol designed for tiny sensors and bad networks.

An MX record tells the internet where to deliver emails for your domain. When someone sends an email to you@yoursite.

Message Framing is how you tell where one message ends and the next begins in a stream of bytes. TCP gives you a stream, not messages.

Multiplexing sends multiple requests over a single connection simultaneously.

NAT is how your home router lets all your devices share one public IP address. Your phone, laptop, and TV each get a private IP (192.168.x.

A nameserver is the specific server that actually knows all the DNS records for your domain — it's the authoritative source of truth.

POP3 is the old-school way to receive email. It downloads all your emails to your device and (by default) deletes them from the server.

A packet is a small chunk of data with an envelope around it.

A path parameter is a variable embedded directly in the URL path. Instead of '?id=5', you put the value right in the path: '/users/5'.

Payload is the actual data carried in a request or response — the valuable cargo.

Ping is the simplest network test — you shout at a server ('hello?') and measure how long it takes to shout back ('yo!').

Polling is the 'are we there yet?' of web development. Your client keeps asking the server 'any updates? any updates? any updates?' at regular intervals.

A protocol is just an agreed set of rules for how two parties communicate.

Protocol Buffers (protobuf) is Google's way of serializing data that's way smaller and faster than JSON. You define your data structure in a .

A proxy is a middleman between you and the internet.

Proxy Protocol passes the real client IP through load balancers and proxies without modifying the HTTP headers.

QUIC is Google's invention that takes the speed of UDP and adds the reliability of TCP, all while encrypting everything.

A query string is the part of a URL after the question mark.

A redirect is when a server says 'what you want isn't here, go look over there instead.' Your browser automatically follows to the new URL.

A request is what your browser (or app) sends to a server when it wants something. 'Give me the homepage.' 'Give me that image.

A response is what the server sends back after receiving a request.

Retry Logic automatically retries failed requests instead of giving up on the first failure. But done wrong, retries cause thundering herds.

A reverse proxy sits in front of your servers and handles incoming traffic on their behalf.

Round Robin is the simplest load balancing strategy: send request 1 to server A, request 2 to server B, request 3 to server C, then back to server A, and s...

SFTP is file transfer done the secure way. It uses SSH to encrypt everything — your password, the files, all of it.

SMTP is the protocol email uses to leave your device and travel to the recipient's mail server.

SSH is like a secure remote control for servers.

Server push is when the server sends data to the client without being asked. Instead of the client constantly asking 'any updates?' the server says 'here,

Server-Sent Events (SSE) is a one-way stream from server to browser over plain HTTP. The server pushes updates, the client just listens.

In a microservices system, every service needs to handle retries, timeouts, mutual TLS, and send traces. You could code all that in every service.

A Service Mesh is an invisible infrastructure layer that handles all the boring-but-critical stuff between your microservices: encryption, retries, load ba...

A session is the server's way of remembering who you are across multiple requests.

A socket is the combination of an IP address plus a port number — it's the complete 'address' for a specific connection.

An HTTP status code is the server's one-line verdict on your request. 200 means 'perfect, here's what you asked for.' 404 means 'can't find it.

Sticky sessions make sure a user always gets routed to the SAME server, like getting the same cashier every time you visit a store.

Sticky Sessions route all requests from the same user to the same backend server. Once you connect to Server A, you always go to Server A.

Streaming Protocols deliver data continuously instead of in one big chunk.

A subnet is a smaller chunk of a larger network, like dividing a city into neighborhoods. All devices in a subnet can talk to each other directly.

TCP is like sending a package with delivery confirmation.

The TCP handshake is the 'are you ready?' dance before TCP data flows. It's a three-step process: your computer says 'SYN' (hello?

The TLS handshake is the 'hello, do we trust each other?' ceremony that happens before any HTTPS data flows.

TTL is how long DNS resolvers are allowed to remember (cache) your DNS records before checking again. A TTL of 3600 means 'remember this for 1 hour.

A TXT record is a free-form DNS record where you can store any text.

The three-way handshake is the official name for how TCP sets up a connection in exactly three steps: SYN, SYN-ACK, ACK.

Traceroute is like ping but it shows you every stop along the way. When your data travels from your computer to a server, it hops through many routers.

A tunnel is when you wrap one type of network traffic inside another. Imagine mailing a letter inside another letter.

UDP is like shouting information across a room — fast but no guarantee anyone heard you. There's no handshake, no confirmation.

A URI is the general term for any identifier of a resource. URLs are URIs that tell you WHERE and HOW to get something.

A URL is the complete web address of something on the internet — the full 'how to get there' including the protocol, domain, path, and any query parameters...

A URN names something uniquely without saying where to find it.

A VPN creates an encrypted tunnel from your device to a server somewhere else.

WebRTC is how your browser does video calls, screen sharing, and peer-to-peer connections without any plugins.

WebSocket is like upgrading a walkie-talkie from push-to-talk to a full phone call.

WebSockets aren't the only way to do real-time. Server-Sent Events for one-way streaming. Long Polling for simple compatibility.

WebTransport is the next-gen alternative to WebSockets, built on HTTP/3 and QUIC.

gRPC-Web lets browsers talk gRPC to your backend.