Unique ID Generator

COMMON

Unique ID generator design is asked at Twitter, Discord, and Meta because it packs distributed-systems judgment into the smallest possible surface: 64 bits. It is the Snowflake design behind every tweet, Discord message, and Instagram photo ID. You will budget the 64 bits (41 timestamp + 10 worker + 12 sequence), handle the clock that steps backward without ever minting a duplicate, assign worker IDs with leases and fencing deadlines, and beat the real bottleneck: RPC overhead, not bit arithmetic: with batching and library embedding.

Budget 64 bits (1+41+10+12) and explain what each field buys: and how Sonyflake tunes the split
Handle backward clock steps with the spin/refuse/borrow ladder: loud beats wrong
Assign worker IDs with ephemeral leases and fencing deadlines that survive GC pauses

TwitterDiscordMetaInstagramSonyBaidu

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Visual Solutions

Step-by-step animated walkthroughs with capacity estimation, API design, database schema, and failure modes built in.

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Cheat Sheet

Key concepts, trade-offs, and quick-reference notes for ID Generator. Everything you need at a glance.

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Anti-Patterns

Common design mistakes candidates make. Wrong approaches vs correct approaches for each trap.

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Failure Modes

What breaks in production, how to detect it, and how to fix it. Detection metrics, mitigations, and severity ratings.

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Difficulty Ladder

Start simple. Build to staff-level.

Level 1

Junior / Basics

Core concepts, single-service design, straightforward requirements

Level 2

Mid-Level Interview

Multi-service architecture, trade-off discussions, standard scaling

Level 3

Senior / Deep Dive

Complex distributed systems, failure modes, consistency guarantees

Level 4

Staff+ / FAANG Hard

Planet-scale design, novel architectures, cross-cutting concerns

Elevator Pitch3-minute interview summary

“I would design a Snowflake-class generator: 64-bit IDs from 41 timestamp bits (69.7 years from a custom epoch), 10 worker bits (1,024 coordination-free minters), and 12 sequence bits (4,096 per millisecond per worker, a 4.2 billion/sec cluster ceiling). Demand of 10M IDs/sec is 0.24% of the bits: the real ceiling is RPC, so batch-500 calls and library embedding serve the platform on 12 workers. Clocks that step backward hit a policy ladder: spin-wait under 20ms, refuse and page beyond, because a paused generator beats a duplicating one. Worker IDs come from ephemeral leases with fencing deadlines that survive GC pauses, and a 1-in-1,000 SETNX canary continuously proves uniqueness.”

Concepts Unlocked8 concepts in this topic