#design

Route requests to the nearest healthy data center

CodingMedium

▲ 00 solutions

Alert routing service with silences and escalation

CodingMedium

▲ 01 solution

Indexed sequence with checkpoints

CodingMedium

▲ 01 solution

Key-value store with constant-time set-all

CodingMedium

▲ 00 solutions

Key-value store that reports its recent request rate

CodingMedium

▲ 00 solutions

Single-threaded scheduler for one-shot, delayed and periodic tasks

CodingMedium

Applied Intuition

▲ 00 solutions

Read-through and write-through cache adapter

Coding

▲ 00 solutions

Recipe shopping cart with bulk discounts

Coding

▲ 00 solutions

Cart with nested transactions

CodingMedium

▲ 01 solution

Shopping cart with discounts, undo and redo

CodingMedium

▲ 01 solution

Access log storage with time range queries

Coding

▲ 00 solutions

Recipe storage with version history

Coding

▲ 00 solutions

Ordered integer stream

CodingEasy

▲ 01 solution

Pluggable hierarchical rate limiter

CodingMedium

▲ 01 solution

Transactional in-memory key-value database

CodingHard

▲ 01 solution

Todo list system design in code

▲ 00 solutions

Page permission management

CodingMediumNNotion

▲ 01 solution

Stepwise DNS resolver with aliasing

CodingMedium

▲ 01 solution

Simplified filesystem with paths and traversal

CodingMedium

▲ 01 solution

Bank ledger with two-step transfers and merges

CodingMedium

▲ 01 solution

Anthropic OA: leveled in-memory record store

CodingMedium

▲ 01 solution

Disk block writes with limited write cycles

CodingMedium

▲ 01 solution

Weighted cache that evicts the heaviest entries

CodingMedium

▲ 01 solution

URL router with single-segment wildcards

CodingHard

▲ 01 solution

Live top-k best-selling books leaderboard

CodingMedium

▲ 01 solution

Generalized tic-tac-toe with k in a row

CodingMedium

▲ 01 solution

Iterator that yields one array first, then the rest of another

CodingEasy

▲ 01 solution

Recent search history with a size limit

CodingHard

▲ 01 solution

Group booking across properties in one neighborhood

CodingMedium

▲ 01 solution

Cache with expiry, priority and LRU eviction

CodingMedium

▲ 01 solution

Oldest one-time visitor in a login stream

CodingMedium

▲ 01 solution

Queue with constant-time min and max

CodingMedium

▲ 01 solution

Key-value store with prefix search

CodingMedium

▲ 01 solution

IP routing table with longest prefix match

CodingHard

▲ 01 solution

Flatten a 2D array with remove

CodingMedium

▲ 01 solution

Rate-limited event logger

CodingEasy

▲ 01 solution

LRU cache with runtime resizing

CodingMedium

▲ 01 solution

Recent file tracker with date and insertion order

CodingEasy

▲ 01 solution

Rate limiter with multiple sliding-window rules

CodingHard

▲ 01 solution

Sliding-window request rate limiter

CodingMedium

▲ 01 solution

Lazy array with deferred map and indexOf

CodingMedium

▲ 01 solution

Design layer document with undo, redo and batches

CodingMedium

▲ 01 solution

Connect Four game engine with win detection

CodingHard

▲ 01 solution

Banking system with transfers, cashback and account merges

CodingMedium

▲ 01 solution

Connect points that share a row or column

CodingHard

▲ 01 solution

Cloud storage with user quotas and backups

CodingHard

▲ 01 solution

Per-domain sliding-window rate limiter

CodingMedium

▲ 01 solution

Agent to-do list with task dependencies

CodingMedium

▲ 01 solution

Social follow graph with point-in-time snapshots

CodingMedium

▲ 01 solution

Ordered IP firewall with CIDR rules

CodingMedium

▲ 01 solution

GPU credit ledger with out-of-order events

CodingHard

▲ 01 solution

Fault-tolerant work queue with leases and retries

CodingMedium

▲ 01 solution

Hybrid run-length and bit-packing codec

CodingMedium

▲ 01 solution

Radix cache for integer sequences with LRU eviction

CodingMedium

▲ 01 solution

Key-value store with nested transaction rollback

CodingMedium

▲ 01 solution

Temporal key-value store with point-in-time reads and restore

CodingMedium

▲ 01 solution

Customer revenue with referral credit and bottom-k query

CodingMedium

▲ 01 solution

Per-user chat event counts in a sliding window

CodingMedium

▲ 01 solution