System-design

A checksum is a fixed-length string from a cryptographic hash that verifies data integrity in distributed systems. It helps detect corruption during data transfer, ensuring clients receive error-free data or can request a clean copy.

Checksums play a key role in data integrity, error detection, secure storage, and password verification. They help detect corrupted data, verify downloads, secure passwords, and prevent duplicates in storage systems.

The Leader and Follower pattern improves consistency and availability in distributed systems by electing a single leader to handle all write operations and coordinate replication, while followers act as backups or serve read requests.

Learn how heartbeat signals help detect server failures in distributed systems. Understand why regular status checks are critical for routing requests and maintaining system reliability.

A Composite Index combines two or more columns into a single index to speed up queries filtering or sorting by multiple fields. Column order matters, and the index supports queries starting with the leftmost column(s).