Introduction

Most countries around the world require a sequential ID or code for business documents like invoices to make them easier to follow. This service, solves that problem.

Generating sequential numbers is more complex that it might seem at first glance. For simple use-cases, a counter field inside a standard relational database is probably sufficient, the problem however is once your project scales and you need guarantees that requests from distributed systems will continue to generate numbers without skips or duplication.

Our Sequence service is designed and built to be highly resilient. Behind the scenes we use a global transaction database (CockroachDB) to ensure data is stored reliably, along with our own layers of queues and processes that ensure a single process is responsible for handling any given sequence. This means our systems can receive a high volume of requests at the same time, and still reliably return numbers in series.

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Key Concepts

The sequence service contains two key objects:

• Series - the definition of a code template.

• Entry - a single “entry” in the series.

These are described in the following sections.

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OpenAPI

The Sequence OpenAPI 3.0 definition is available for download in YAML here: