Token Bucket The token bucket algorithm models a bucket of capacity B tokens that refills at rate R tokens per […]

Trie Node Structure Each node in a trie holds a fixed-size array of 26 child pointers (one per lowercase letter)

Compare-and-Swap (CAS) Compare-and-Swap is the atomic instruction at the heart of all lock-free algorithms. It takes three operands: a memory

Mutex Basics A mutex (mutual exclusion lock) guarantees that only one thread can hold it at any given time. The

Stack vs Heap Allocation Every running program uses two distinct memory regions for dynamic data: the stack and the heap.

Three-Way Handshake Every TCP connection begins with a three-way handshake that establishes synchronized sequence numbers on both sides and verifies

Write Path Every write in an LSM-tree storage engine lands first in two places simultaneously: the in-memory MemTable and the

B-Tree Node Structure A B-tree of minimum degree t enforces a capacity invariant on every node except the root: each

Core Problem LFU (Least Frequently Used) is a cache eviction policy that removes the item with the lowest access frequency

Core Data Structure An LRU cache combines two data structures to achieve O(1) time for every operation. The doubly linked

Provider Schedule Model A provider’s schedule is defined at two levels: recurring availability rules and date-specific overrides. Recurring rules describe

Double-Entry Accounting A digital wallet is a ledger, and the correct foundation for any ledger is double-entry accounting. Every financial