What Is Webhook Fan-Out? Webhook fan-out is the process of delivering a single event to multiple registered external endpoints (webhooks). […]

What Is a User Segmentation Engine? A user segmentation engine partitions a user base into named groups (segments) based on

Columnar vs Row Storage: The Fundamental Tradeoff In a row-oriented storage engine (PostgreSQL, MySQL, SQL Server), all column values for

What Is a Bitmap Index? A bitmap index represents the presence or absence of a column value for each row

Why B-Trees Cannot Index 2D Space A B-tree sorts data along a single dimension. Given a point (lat, lng), there

What Is an Inverted Index? An inverted index maps each term (word or token) to the list of documents that

B-Tree Structure and Page Layout A B-tree index is a balanced tree where every node is a fixed-size disk page

LSM Tree Structure and the Need for Compaction A Log-Structured Merge-tree (LSM-tree) accepts all writes into an in-memory buffer (MemTable).

What Is a Write-Ahead Log and Why Does It Exist? A write-ahead log (WAL) is the foundation of durability in

MVCC (Multi-Version Concurrency Control) is the foundation of concurrent transaction processing in PostgreSQL, MySQL InnoDB, Oracle, and most modern distributed

Snapshot isolation (SI) is the transaction isolation level used by PostgreSQL (as its default), Oracle, SQL Server, and many distributed

Raft is the consensus algorithm designed to be understandable. It powers etcd (Kubernetes backbone), CockroachDB, TiKV, and many other systems

The gossip protocol is the distributed systems equivalent of rumor spreading: each node periodically shares information with a small random

Counting the number of distinct elements in a large stream — cardinality estimation — seems to require storing every unique

A bloom filter is a space-efficient probabilistic data structure that answers membership queries with certainty about absence and high confidence