Resources for the Clojure programming language

Clojure is a modern, functional Lisp dialect that runs on the JVM, designed for simplicity, robustness, and concurrency. Created by Rich Hickey, Clojure emphasizes immutability and data-driven programming, making it well-suited for building scalable, fault-tolerant systems.

With its minimalist syntax and powerful macro system, Clojure encourages expressive, concise code while leveraging the full ecosystem of Java libraries. It also features built-in support for immutable data structures and software transactional memory, making it a strong choice for concurrent programming.

Clojure is widely used in web development, data processing, and distributed systems, appealing to those who appreciate Lisp’s elegance combined with the practical benefits of modern tooling.

Griffin: Building a Regulated UK Bank from Scratch with Clojure

Griffin is a fully-regulated UK bank offering banking-as-a-service through APIs, enabling fintech companies to integrate banking capabilities into their products. After receiving their UK banking license from the Financial Conduct Authority in March 2023, they faced the challenge of building a complete banking platform that could process real financial transactions with absolute reliability. Operating with approximately 24 engineers across the UK and Europe, they needed technology that would both attract exceptional talent and provide the correctness guarantees essential for managing customer funds.

The technical leadership selected Clojure for its immutability and natural fit with financial systems requiring comprehensive audit trails. Griffin's architecture centers on event sourcing built atop FoundationDB, the same strict-serializable database Apple relies on for iCloud infrastructure. Every API call and external webhook becomes an event processed by hundreds of independent processors, with business logic implemented as pure functions isolated from side effects. This design enables formal reasoning about system behavior and satisfies the operational resilience standards demanded by banking regulators.

The language choice delivered unexpected recruiting benefits: while generic enterprise languages attract massive applicant pools with low signal-to-noise ratios, Clojure applications consistently yielded higher-quality candidates. Griffin's experience as a distributed team demonstrates that mid-sized engineering organizations can build and operate mission-critical financial infrastructure in functional languages. These are systems where data integrity and continuous availability aren't negotiable requirements but fundamental constraints.