GraphQL Sydney February 2022

Welcome to the February 2022 online edition of GraphQL Sydney, our first meetup for the year!

To kick us off, we have:

A GraphQL-based Schema Architecture for Microservices

• Jean-Jacques Dubray :: @metapgmr

Message and Event payload validation has been a rather thorny problem to deal with for the past 20+ years. Several generations of Schema definition languages such as DTD, XML-schema, json-schema, OpenAPI have tried to solve that problem but their structure remains unfamiliar to most developers and often result in a rather anemic set of validation rules (such as every field is optional), leading to a perceived low value, and therefore a lack of interest.

Regardless of the schema language, there are three key problems in a schema architecture:

• the reusability of data structure definitions
• the expressivity of the schema language
• the developer experience

Nav is a Small Business Lending platform built on a polyglot microservice architecture, complemented by an event bus. It is essential for us to develop a consistent way to validate our message payloads (APIs and events) across all microservices. Considering that it has one of the best DevX in the industry, we got the idea to use GraphQL as a schema language without any runtime component. After all, a GraphQL query describes the payload requested by a client, so why not use the same syntax to create a message definition and generate client-side and server-side validation code?

Nav’s Schema Architecture has been used in production since last September and we can already see some of the key benefits:

• Rich validation rules
• A consistent set of validation rules regardless of the language (Golang, Python, Ruby and JSON-schema).
• An intuitive DevX that allows us to onboard engineers very quickly
• A communication mechanism that conveys easily and precisely reusable data types across all payloads
• A massive productivity gain with a 10-20X compression factor between the payload definition and the amount of generated code

These benefits proved to be very useful in the implementation of our event-driven architecture. We are now using for gRPC and protobuf as well.