Tutorials

Server-Sent Events let a server push data to a browser over an HTTP connection that never closes. It’s simpler than WebSocket, comes with automatic reconnection built in, and it’s the same format used by language model streaming APIs.

WebSocket is the protocol that keeps a connection open between browser and server so both sides can send data at any time. This article explains the handshake, frame structure, and how to implement it step by step with Node.js.

The QUIC protocol runs over UDP and eliminates the slow handshake of separate TCP plus TLS negotiations, letting HTTP/3 open connections in a single round trip or even zero. This guide explains how it works internally, how to test it with curl and nginx, and when it makes sense over HTTP/2.

CORS is the policy that decides whether the browser hands over an API response to a script running on another domain. This guide explains the preflight mechanism, the exact headers you need, and the most common configuration mistakes.

GraphQL is a query language that lets the client request exactly the data it needs, without over-fetching or chaining multiple calls. This guide explains how it works internally, with code examples and an honest comparison with REST.

A JWT token lets a server confirm who you are without querying the database again on every request. This guide explains its structure, how to sign it with Node.js, and its real security risks.

Regex engines aren’t magic: they parse the pattern, build an automaton, and run it against the text. This article explains how they work internally, why some are vulnerable to ReDoS, and when it makes sense to switch to an automaton-based engine like RE2.

Skip lists are a probabilistic data structure that Redis uses to implement sorted sets and that LevelDB uses in its MemTable. Instead of balancing a tree with rotations, each node flips a coin to decide how many levels of shortcuts to have. The result is expected O(log n) performance with an implementation much simpler than an AVL or red-black tree.

LSM trees are the data structure that lets RocksDB, Cassandra, and LevelDB handle intensive writes without rewriting existing files. This article explains memtable, WAL, SSTables, and compaction with real code examples and commands.