Selling Clojure to the Business

Our experiences of selling Clojure

Selling Clojure to the Business

March 30, 2015
Jon Pither

When JUXT talks to potential clients we're often trying to answer 'Why Clojure?' Here I will attempt to cover some of the answers we have evolved through various sales meetings. Feel free to use what's here or to provide feedback. For those wanting Clojure to play a leading role in shaking the IT industry out of its wasteful malaise, then we're all in this together.

Clojure is Lean

Developers love Clojure for it's simplicity and well thought out approach to immutability with its persistent data collections. This is fantastic and absolutely valid, but if we're in a meeting with business stakeholders then it's better to lead with how Clojure helps development teams get more done with less.

Clojure is leaner than other mainstream languages, and this should be the first killer answer to the 'Why Clojure?' question.

To back this up we talk about past Clojure projects. At a Clojure rewrite of an online newspaper the existing Java solution was around 500k lines of code, the Clojure replacement being ~20K LOC solution. There was an analogous previous attempt to rewrite the platform in Java using XLST but this was terminated after a couple of years. The Clojure effort took about six months with a small team of high motivated developers and was utterly successful.

At a major property portal we built and released 4 fully-fledged systems in under 10 months from scratch. We have seen from other Clojure projects outside of JUXT that this is a repeating pattern; Clojure is an extremely powerful weapon for productivity. You can achieve more with less; Clojure codebases tend to be an order of magnitude less in size than their mainstream counterparts.

Yes, Clojure is a beautiful, elegant language to work with. More importantly for businesses though, it's extremely effective for building software against tight timescales.

Why is Clojure Lean?

The person opposite will be wondering why is Clojure so lean and effective? You may think it's unsporting and a bit negative to shoot fish in a barrel, but here I like to attack OO a bit. You can't avoid this anyway as OO is the elephant in the room being the mainstream status quo. I've have found however that this can be a light and fun conversation, as people generally enjoy trading war stories and rallying against established orthodoxy.

We usually open by discussing how in OO we tend to preemptively build up a comprehensive object model to describe the problem domain exhaustively. Objects for everything, let no minutiae detail of the business domain go unmodelled, unformalised, unclassified. The object model adds reams of code to the solution and generates a class of second order problems such as constant maintenance and dependency management. Sure, it may not be idiomatic in OO to create masses of type classes at low abstraction levels, but we're talking mainstream here. It happens all the time and leads to colossal waste on software projects.

In Clojure we work with the data as it comes using inbuilt basic collection types; maps, sets, vectors etc. We operate on the data using simple functions to achieve transformational logic, functions being simple data-in, data-out contracts with no side effects. We offer that this is a much simpler way of going about programming and gets us closer to working functionality faster.

Functional and an Evolving Domain Model

Sometimes I can see an element of 'better the devil you know' creeping into the conversation with the person opposite. The potential client may well be thinking "OK, whilst I'm not a massive fan of big object models, I'm not sure I like this idealised future of mathematical functions manipulating raw data all the time... it does sound like a rather sterile and soulless future. What about the value of having a domain model in the code? Hasn't everyone has bought into Domain Driven Design, where the code makes some attempt to promote a common understanding between developers and business stakeholders?"

I like to address this counter-argument on the front foot. The domain model evolves from composing functions together and creating high order functions that clearly express the business rules they are serving. With a functional codebase, the domain model is more apparent as business rules sit closer together in well defined namespaces as simple functions, rather than being scattered about in large type definitions.

It can be difficult not to get carried away when arguing this point. I want to express how in Clojure a codebase tends to evolve the domain model organically, adhering to bottom-up development principles. On the surface a mature Clojure codebase acts like a DSL on steroids, the result being a beautiful business language sitting on top of the baseline fundamental language of Clojure.

OK, but why Clojure? Isn't Clojure a bit esoteric?

People have often have a cynical view of salesmen peddling obscure tools and technologies. They may have heard that Clojure is a LISP, and so they could have pre-judged it as an esoteric developer fad.

We say that Clojure is a safe choice for the enterprise after all. It's built on Java; you can deploy it to your existing Java ecosystem and use your existing Java libraries. We see Clojure as pragmatic; yes it's strongly opinionated but it won't stop you adding occasional side effects into your functions and it doesn't get in your way. There are some pure functional languages out there that do have a more rigorous academic grounding, but Clojure is a language that is meant to be widely used, and is becoming so.

What's the size of the development pool, is it easy to hire Clojurians?

Our past clients haven't had any difficulty hiring, and what they usually report is that they see a higher calibre of individuals coming through the door. I'm a little wary of over-selling this point as there's never a free lunch when it comes to hiring, and the point can sound a little arrogant. But it is true nonetheless; the available resource pool of Clojure developers is self-selecting. You get enthused technologists extremely passionate about what they do, or else they would have stuck with the mainstream.

This point gets a lot of traction with potential clients. I can only conclude that every IT business struggles with recruitment. If having a language like Clojure will actually help the process, then they want to consider it.

We talk specifically about the great community spirit in Clojure, and of the frequent regional meet-ups happening in multiple countries.

This conversation is usually interlocked with a concern about training. We say we've never had any problem training up Clojure developers, and developers making the leap tend to love it and never want to go back. This helps hugely with staff retention.

Energising a company

This is a point we sometimes make, depending on the context. We do want to cover that Clojure is a fun programming language, and that it can be used as a mechanism to re-energise an IT department.

We're seeing lots of cases of IT departments feeling stuck and inefficient. Not all stakeholders are adverse to disruption, many require and seek it.


There are many more tangents and deviations than what we've covered here, and it does require discipline to stay focused. We hope this post gives some ammunition to others trying to sell Clojure, either externally or internally.