Introducing PostgREST, a REST API for any PostgreSQL database written in Haskell

2 min read

Written in Haskell, PostgREST is a standalone web server that enables you to turn your existing PostgreSQL database into a RESTful API. It offers you a much “cleaner, more standards-compliant, faster AP than you are likely to write from scratch.”

The PostgREST documentation describes it as an “alternative to manual CRUD programming.” Explaining the motivation behind this tool, the documentation reads, “Writing business logic often duplicates, ignores or hobbles database structure. Object-relational mapping is a leaky abstraction leading to slow imperative code. The PostgREST philosophy establishes a single declarative source of truth: the data itself.”

Performant by design

In terms of performance, PostgREST shows subsecond response times for up to 2000 requests/sec on Heroku free tier. The main contributor to this impressive performance is its Haskell implementation using the Warp HTTP server. To maintain fast response times, it delegates most of the calculation part to the database including serializing JSON responses directly in SQL, data validation, and more. Along with that, it takes the help of the Hasql library to efficiently use the database.

A single declarative source of truth for security

PostgREST is responsible for handling authentication via JSON Web Tokens. You can also build other forms of authentication on top of the JWT primitive. It delegates authorization to the role information defined in the database to ensure there is a single declarative source of truth for security.

Data integrity

PostgREST does not rely on an Object Relational Mapper (ORM) and custom imperative coding. Instead, developers need to put declarative constraints directly into their database preventing any kind of data corruption.

In a Hacker News discussion, many users praised the tool. “I think PostgREST is the first big tool written in Haskell that I’ve used in production. From my experience, it’s flawless. Kudos to the team,” a user commented.

Some others also expressed that using this tool for systems in production can further complicate things. A user added, “Somebody in our team put this on production. I guess this solution has some merits if you need something quick, but in the long run it turned out to be painful. It’s basically SQL over REST. Additionally, your DB schema becomes your API schema and that either means you force one for the purposes of the other or you build DB views to fix that.”

You can read about PostgREST on its official website. Also, check out its GitHub repository.

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