A scalable service to generate time-ordered, unique ID numbers.

Link to this section Overview

This is a service to generate Snowflake IDs. These are unique, time-ordered IDs, useful for things like instant messages or posts.

Link to this section Motivation

I wanted to get more experience working with the 12 Factor App model. Implementing a basic service like this seemed like the easiest way to go about it. I also figured this kind of service could be useful for me at some point.

Link to this section Technical Description

The "Snowflake" ID format was designed at Twitter for identifying tweets, so its scalability is its main selling point. Each Snowflake is a 64-bit integer composed of a timestamp in milliseconds (42 bits), worker ID (10 bits), and increment (12 bits).

The format can support 1024 possible worker IDs -- too many to hardcode by hand, but too few to assign randomly. So, I made a second app, "SnowCloud," that handles the assignment of these worker IDs to the Snowflake server instances. When a Snowflake server comes online, it will request a worker ID from a SnowCloud server. Then, it will periodically renew the worker ID with the SnowCloud server. The pool of worker IDs are stored as a Redis set, sorted by how recently each was used. In addition, each Snowflake server is identified by a UUID, and these UUIDs are tracked to ensure Snowflake servers can only renew their own assignments. (For reference, the SnowCloud repo is at, predictably, Breq16/snowcloud.)

Link to this section Results

It does everything I set out to accomplish, and I got more experience developing microservices, which was cool. This was just a quick afternoon project--it was cool to go from idea to finished product in just a couple hours.