Case Studies
Unique Distributed ID Generator
Composite timestamp + node-ID + sequence IDs (Snowflake-style) — unique and roughly time-sortable with no central counter, plus real clock-skew handling.
Designing the small service every other write in a distributed system quietly depends on: handing out an ID that's unique across every node and every region generating them at the same time, with no central counter to bottleneck on — while keeping IDs roughly ordered by creation time, since pagination, message ordering, and sharded lookups all lean on that ordering without saying so.
What this lesson covers
A 64-bit ID of millisecond timestamp, node ID, and per-node sequence (Snowflake-style), minted in-process with no network call, is unique across nodes and roughly time-sortable. Assign node IDs via a coordination service and handle a clock stepping backward.
- A database auto-increment column is perfectly unique right up until there is more than one writer; then it is a bottleneck.
- IDs must be unique across every node and region, roughly ordered by creation time, and minted without a round trip per request.
- The trick is giving each generator its own disjoint slice of the ID space up front, so uniqueness needs no per-request coordination.
- A raw UUID gets uniqueness but gives up sortability, which pagination and sharded lookups quietly depend on.
- Senior answers raise node-ID assignment and a clock stepping backward unprompted; staff adds multi-region uniqueness.
Included in Plus and Pro
Continue reading “Unique Distributed ID Generator”
The full lesson works the design through end to end — diagrams, trade-offs, and what interviewers expect at each level. About 18 minutes.
- Understanding the Problem
- Functional Requirements
- Non-Functional Requirements
- Capacity Estimation
- Core Entities
- API Interface
- High-Level Design
- Trade-offs
- Final Design
- Operations & Observability
- Level Expectations
- Follow-Up Questions
- Try It Yourself