Production Lisp in 2020?

Yep, I've used Common Lisp in production. Several times. I'm in the middle of writing a new app with Lispworks right now.

Common Lisp is generally the first thing I think of for any new work I undertake. There are exceptions, but usually my first choice is Common Lisp. It has been for a little over thirty years.

I've often worked in other languages--usually because someone wants to pay me to do so. I usually pick Common Lisp, though, when the choice of tools is up to me, unless some specific requirement dictates otherwise.

The objections you list might be an issue to some extent, but not much of one. Certainly not enough to discourage me from using Common Lisp in a pretty wide variety of projects. I've used it for native desktop apps, for web apps, for system programming, for text editors, for interpreters and compilers. When I worked on an experimental OS for Apple, the compiler and runtime system I used were built in Common Lisp.

I'll use something else when someone pays me enough to do it. I'll use something else because it's clearly the best fit for some specific set of requirements. I'll use it when there isn't a suitable Common Lisp implementation for what I want to do. I'll even use something else just because I want to get to know it better.

I've taken various detours along the way into learning and using various other languages. I like several of them quite a bit. I just don't like them as much as Common Lisp.

The pleasure I take in my work is a significant factor in my productivity. Choosing tools that offer me less joy is a cost I prefer not to bear without good reason. That cost often exceeds the advantage I might realize from using some other language. Not always; but often.

There was once a language I liked even better than Common Lisp. Apple initially called it 'Ralph'. It evolved into Dylan, which, in its present form, I don't like as much as Common Lisp. If I or someone else invested the considerable time and effort needed to write a modern version of Ralph, then I might choose it over Common Lisp.

For now, though, I'll stick with the old favorite. It continues to deliver the goods.

I think Reddit's decision to move from Common Lisp to Python is interesting and their reasoning (ecosystem) is still valid 15 years later.

The historical timeline is especially interesting because Reddit's cofounders Steve Huffman & Aaron Swartz were alumni of Paul Graham's first YC batch and PG is the author of the well-known Lisp essay "Beating the Averages":

- 2001-04 Paul Graham : Lisp essay "Beating the Averages" [1]

- 2005-07-26 Paul Graham : https://groups.google.com/forum/#!topic/comp.lang.lisp/vJmLV...

- 2005-12-05 Steve Huffman : https://redditblog.com/2005/12/05/on-lisp/

- 2005-12-06 Aaron Schwartz : http://www.aaronsw.com/weblog/rewritingreddit

The takeaway from the Reddit case study is this: Yes Lisp macros and language malleability gives it superpowers that other languages don't have (the "Blub Paradox") -- but other languages also have other superpowers (ecosystem/libraries) that can cancel out the power of Lisp macros.

You have to analyze your personal project to predict if the ecosystem matters more than Lisp's elegant syntax powers.

[1] http://www.paulgraham.com/avg.html

I'm using Lisp in production, our browser and all of our infrastructure is in Lisp https://github.com/atlas-engineer/next.

TO address some of your points;

poor ecosystem of libraries: many great libraries, some incomplete. you must not be afraid to look at the source code to understand and edit

poor community coordination: true, there are few large scale community lisp projects. be the change you want to see

dependency limitations with quicklisp: like what? quicklisp works great. if you are talking about loading several versions of the same library at the same time in a single image, this is being researched and developed

poor support for json: no, there is good support

have to restart the server every 20 days: not familiar, I have had lisp servers running for years now

hack to tune GC: no

if I had to redo my project would I choose Lisp? I would choose lisp, yes. there is no more powerful language than this, and believe me, I have tried many

Clojure has a good ecosystem and you can fall back to Java's ecosystem if needed. It has excellent support for json, and acceptable async support (I use manifold + aleph, but there are other options). It runs on the JVM which has world class GC.

I delived a service in 2019 that was written 100% written in clojure. ReactNative app + SPA Web app + Server all sharing the same code.

The developer experience was great. I get subsecond hot-reload on all plataforms (app emulator/app on-device/web/server).

The same UI components was shared between ReactNative and ReactDOM. All App issues are reproducible in Web, then I fix in web and I'm sure that App is working.

Even SSR was possible, with some tweaks.

CircleCI is mostly Clojure, and some Go.

The only problems we are seeing is the significant startup time cost (hence the Go bits, where it matters).

Memory usage also isn't always great, but that's more a JVM problem, as it's not releasing reclaimed memory as quickly as you'd like it to. Fine on servers, annoying on a 16GB laptop.

The Common Lisp problems you outlined don't really apply to Clojure, it's a modern lanaguage and has been stable and versatile for us.

Rigetti Computing is a company that builds quantum computers.

We have used Common Lisp in production at Rigetti Computing for 4 years both in cloud deployment as well as for a downloadable SDK. Common Lisp is used to build what is currently the best free optimizing compiler for quantum computing [1, 2] as well as one of the most flexible quantum computer simulators [3]. They’re both open source, so you can actually see for yourself how we version, deploy as binaries, and deploy in Docker containers.

> If you are using lisp in production for non-trivial cases, do these issues still exist?

Before getting into the specifics, any large, non-trivial product that customers use will need tweaking. Especially languages that have runtimes, including languages like C. This is usually a result of leaky abstractions that just have to be dealt with in The Real World (TM).

> * poor ecosystem of libraries - few gems, most other half-baked

You have libraries for most things you need. Some are lacking, like in scientific computing. But all your usual stuff to glue things together is there and works.

Some people confuse “half-baked” with “no commits for 5 years”. Lisp libraries are older than many in vogue languages, and Lisp doesn’t change, so “5 years no commits” shouldn’t be worrisome.

At Rigetti, the biggest weight we had to pull that we wouldn’t have needed to do in, say, Python, is bind to a bunch of FORTRAN code, specifically LAPACK. That was a pain because you need to do FFI with complex double floats.

* poor community coordination

The community all agrees on one thing: Lisp is standardized.

Lisp lacks a sort of “centralized community” like Go or Clojure. I like to think that Common Lisp is more “democratic”. We have a “constitution” (the Common Lisp standard) that we all agree on and we all make our own contributions atop that.

With that said, #lisp on Freenode is attentive. SBCL, for example, responds to bug reports almost immediately. Several library ecosystems are kept up to date, etc.

> * Dependency management limitations with quicklisp

With Quicklisp, I personally realized a lot of other dependency management solutions are overblown and don’t actually solve problems. Maybe QL gets away with it because the ecosystem is smaller than others.

Xach, the creator of QL, does a lot of community diligence for free to ensure things work.

For production code, I’ve had 0 issues.

> * poor support for json

We use YASON [4] and it works fine.

> * poor support for async

This is true now but wasn’t true years ago. Lisp implementers have not been interested in implementing a runtime supporting async programming. Little in the Common Lisp language itself prohibits it. Before the world of threads and SMP, Lisp implementers did implement async runtimes.

Why aren’t Lisp implementers interested in async? I’m not sure. Maybe they see it as a passing fad?

> * have to restart the server every 20 days because of some memory leak

Memory leaks can happen but they’re usually the programmer’s fault for not understanding symbol interning, weak pointers, or finalizers. Writing long-running applications does require know-how.

> * hack to tune GC

I don’t consider it hacking. In SBCL we tune the GC to our application. This seems reasonable; different programs have different allocation patterns. But you wouldn’t need to do this out of the box.

> is there a way you can quantify effort is resolving them, and if yes, what is it?

Big applications that are customer products require care and feeding. The benefits of writing in Lisp in the first place largely outweigh some of the extra work needed to productionize it.

I will say that writing production Common Lisp code is greatly benefited by having at least one experienced Lisper on the team. If a team would, for some reason, write an application in Lisp but not really have a good understanding of the language, then productionizing and hardening will be difficult.

> and, finally, if you had to re-do your project, would you chose lisp or something else?

Common Lisp allows something that never existed before (a completely automatic, optimizing quantum compiler) to exist. If Lisp weren’t there, that wouldn’t exist.

My parting advice is this: The biggest difficulty in writing an application is to actually write it. It takes a lot of hard work to get requirements, listen to feedback, articulate a direction, etc. In Common Lisp, SBCL or LispWorks or whatever else, dumping an executable is so easy and you can have a deployable “production app” in 5 minutes. So the good news is that you won’t be held up trying to figure out how to dockerize your Python app.

I definitely agree that before embarking, doing an objective and relevant comparative analysis would be good (we did this at Rigetti), but ultimately you just need to sit down and write.

Almost every programming problem is solvable these days with enough glue and elbow grease. I wouldn’t be too worried.

[1] https://arxiv.org/abs/2003.13961

[2] https://github.com/rigetti/quilc

[3] https://github.com/rigetti/qvm

[4] https://github.com/phmarek/yason

Perhaps you didn't mention it for a reason, but I am sure I won't be the only one to bring up Clojure in this thread, and others will argue for and against more eloquently. Obviously it lacks much of what makes people love Common Lisp, but it's more Lisp than not Lisp, and specifically addresses all of your points via the JVM and its ecosystem.

I’ve not used lisp in production. But I sometimes wish I did. In particular, whenever there’s an issue with a production process (think a batch job rather than some kind of online processing), I wish I could attach a debugger, inspect some variables, and invoke a restart. I don’t know how of any language that makes it more convenient to do that sort of issue-resolution.

I don’t really care about libraries. I think generally it’s not very hard to write an ffi binding to a C library and most of the time you don’t need a library anyway. Most of the time you can just write your own library from scratch as you probably only need a few functions.

But maybe this is more a statement of the sort of programs I work on and if you worked on different systems you would want to use lots of external libraries that you don’t control.

I think the biggest issue with CL is how tightly attached it is to an outdated standard. It makes it harder to have things like good Unix support if your interface is through pathnames and streams.

Other thing which may be annoying about CL are the lack of a good way to consistently go from source code to a binary and that compiler optimisations can be unpredictable

First, thanks for linking my Living Common Lisp book. Common Lisp is my preferred language, but only for projects where I need/want an environment that support rapid experimentation of new ideas. If I know how to implement something and I want to deploy at scale, then I might not choose Common Lisp.

I am a happy LispWorks customer but I also use SBCL (efficient code, easy to package standalone apps) and Clozure Common Lisp (fast compiler for development).

Can't speak for SBCL (I use it exclusively for development and haven't deployed anything non trivial and user facing with it) but I have used Clozure CL (CCL) successfully to develop back end services without horror stories regarding the GC. If you end up needing huge heap sizes, in theory with ABCL you get access to state of the art GC algorithm implementations and (IMHO) a much nicer, less dogmatic language than Clojure.

I recently switched to LispWorks after struggling a bit with CCL's Cocoa bridge and I wish I had done that sooner. A much younger, idealistic me would scream at the thought of it but sometimes you just need to throw some money at a problem. CAPI is really a killer feature.

We use CL for production (embedded/distributed system). CCL and Lispworks on low end ARM32.

We do use JSON but mainly for the product's Websocket API towards higher level SCADA system. As we have control over both ends there isn't much trouble really.

The project has soft realtime component also implemented with Lisp, and at least Lispworks exposes a substantial degree of control over GC. We however didn't need to tune anything thus far.

The system has perhaps a dozen direct dependencies to the libraries, luckily few of them posed any challenges in use.

Apple has been using Clojure in production for years, and is hiring: https://jobs.apple.com/en-us/details/200000986/apple-media-p...

Excerpt from the description: "These are the people who power the App Store, Apple TV, Apple Music, Apple Podcasts, and Apple Books. And they do it on a massive scale, meeting Apple’s high expectations with high performance to deliver a huge variety of entertainment in over 35 languages to more than 150 countries."

I use lispworks, the CAPI works well on allmost all platforms. They know what they are doing. Books: common lisp recipes, PAIP, ANSI COMMON LISP. The few libraries you need are very good.And you need Quicklisp. I stopped using C, C++, pascal, fortran, javascript. Altough they all are just fine. You still have to learn the craft of programming. Just go for it.

Not really production because the traffic is low, but I run http://ichi.moe on SBCL (Hunchentoot web server) and I never had to restart it because of memory leak or a crash. I usually hot-swap the updates and the same server process stays up for months. It also heavily uses JSON and XML and the libraries for them (jsown and cxml) are perfectly adequate.

I'm starting a new project in Lisp in 2020. That's rolling my own CAD tools for learning hardware development.

Lisp makes sense because it's a comfortable environment for interacting with my data. I'll be running the Lisp code "offline" so I'm not worried about runtime aspects like GC pauses and most of my I/O will be generating data for external tools (e.g. KiCad) in their own esoteric formats.

Coming back to Lisp it's nice to see that all my favourite software is still available and working fine, and there seem to be more active open source Lisp developers than ever. (Far fewer than Javascript, for example, but that's not my yardstick.)

I am running a web app in production, with live reloads, no issues so far.

> * poor ecosystem of libraries - few gems, most other half-baked

I actually had the choice for my libraries: DB interface, email sender, HTML template, data structure helpers… these ones with good documentation.

I have observed and explored the ecosystem for the last 3 years and I still find hidden gems. There are way more libraries than we can see at a quick glance.

We do a selection on https://github.com/CodyReichert/awesome-cl

> * poor community coordination

It looks like the oldest ones don't coordinate much and the youngers do (and push the established players, such as the CL foundation).

> * poor support for async

Maybe not for a full async runtime (cf Turtl feedback), but there is a good choice for all sort of async stuff (bordeaux-threads, lparallel, lfarm, channel, SBCL built-ins etc)

I use Clojure and ClojureScript in production. The developer experience is a real pleasure: there is good library support, libraries are typically easy to use, and you can always interop with the underlying JVM/js if the need arises.

Clojure also has the core.async library. This can be used along with Reagent to build React-based apps; core.async allows you to do what Redux does but in fewer lines of code.

https://github.com/deckeraa/OpenStainer is an example of building apps this way.

Clojure is a production Lisp in 2020

I used to work in Common Lisp (SBCL).

The ecosystem problem meant something different to me than most. Sure, when new tech came out (Kafka to pick a random example) there wouldn’t be an open source library ready for me. But I had stable infrastructure so I didn’t really care much about that.

The ecosystem problem for me meant that if something went wrong I was on my own. It’s a pretty unfortunate feeling to search for a bug and find nothing on Stack Overflow.

I really hope that Lisp will get a comeback in the space that is now occupied by XML and YAML. It's always the same story: Narrow minded engineers chose YAML (formerly XML) as the trendy simple configuration language and it works fine for a while. 3 years later they inevitably hit the ceiling with YAML and either start badly implementing new language features on top of YAML (see Gitlab CI's `when`, `only`, `except`, etc. syntax) that are never flexible enough or write hugely complicated templating tools (see Kustomize and Helm for K8S) for things that would amount to a simple if-expression in Lisp. This is the use case where Lisp can really shine. Configuration is almost always untyped and doesn't start out with a library ecosystem. Most of the time you just need a way to write a simple nestable DSL that is human readable. There's probably no language that makes this simpler than Lisp: Any college freshman could write their own interpreter. But it is also extremely flexible if it turns out that you need more power than YAML offers.

> poor ecosystem of libraries - few gems, most other half-baked

Definitely no longer an issue for Common Lisp. Quicklisp is da bomb.

> Dependency management limitations with quicklisp

Never had any issues. It Just Works for me.

> have to restart the server every 20 days because of some memory leak [3]

You can get memory leaks in any language. You're much less likely to have a leak in a GCd language than a non-GCd language. But seriously, if you can't easily restart your server whenever it's needed, you have bigger problems.

> hack to tune GC [5]

I've run CL in production for many different applications. I've never had to tune a GC.

ITA software's account of using CL may also be of interest,

http://www.paulgraham.com/carl.html

try hy - https://docs.hylang.org/en/stable/

Most of my production code is python, but I also wanted to create a dsl so I used hy. You get to enjoy both worlds

Thank you for your responses. I was interested in learning about these concerns for Common Lisp only, and not the other dialects including scheme, clojure, racket ...

This may not squarely answer your question, but when I was investigating this for a production project, the following tools seemed to be both essential and well-supported.

SBCL, SLIME, SLY, ASDF, quicklisp, and ultralisp

Other tools and solutions are available, but familiarity with this seemed to be what was required for comfortable use.

My very early stage startup, whiplash.gg (tune in today at 2pm PT to see us in action) uses Clojure on the backend.

Ladder Insurance is a full stack Clojure shop and Watchful has a bunch of Clojure in prod too.

I made a few hobby projects in different Lisps, but in the end for my field (REST backends) I would chose Erlang and today I also started looking towards Kotlin. Lisp's macros while being powerful are still creating a lot of trouble in terms of understanding the system, working with other people and finding support online. Also I personally didn't meet many developers who have solid understanding of FP, not even talking about macros - they are simply too complicated and don't allow human scaling.

Have you considered lisp dialects? I've been working with Clojure/Clojurescript for a while and it addresses most of those concerns. It's been a real pleasure to work with.

- There are lots of high quality libraries, but you also have access to the entire Java and/or Javascript ecosystem with very easy interop

- Not too sure what you mean by "community coordination", but I've found the clojure community to be exceptionally friendly, welcoming, and responsive. The core team is active and I've even had some questions answered directly by them in slack!

- There is some tooling built and maintained by the core team that makes managing dependencies painless

- There's a library (transit) that's widely used and well suited for marshalling data in and out of a clojure app. There's a library that's part of the core which implements the CSP (communicating sequential processes) concurrency model, similar to Go. It works in both Clojure and Clojurescript and is a very sensible way to manage async operations in a system.

- GC is managed by the JVM (for clojure), which is state of the art

The problem with malleability of programming languages, is there is no upper limitation of how malleable it can be.

I experienced this in both Clojure and Ruby as well. The fact that developers can spend countless of precious time, cycling through a loop of malleability, reforming an already functional product in production. It costs precious time and money, it is expensive. And more importantly, it is non-stop.

Other programming languages like Go are very conservative with feature changes, and imposes hard limitations by choice, the team/company behind it thinks the same way, that a cycle of O(n) is destructive.

And nowadays, you can't expect a developer to stay on a company for so long, so a sureball tooling to hit it hard, and precise, with less time and tinkering around is much needed than ever.

On the future of programming languages, we will see languages being used not because it is malleable, but because it is sure, precise and right for the job.

I'm using Hy[0] for some API-accessible "glue code" (basically doing high level stuff with scipy.sparse and friends as building blocks).

[0] hylang.org

Your questions are well answered by Paul Graham in http://www.paulgraham.com/avg.html.

There are many Common Lisp and Scheme environments. Many have excellent JIT compilers. They all have their relative strengths and weaknesses. So it really depends on your specific use case as to which environment has the best support. For me the biggest factor is that Lisp is very productive for use by a small and competent team. In those situations they tend to create a DSL and evolve the system. PG's essay describes the reason Lisp fails many projects in the section "The Blub Paradox".

I use CCL and a set of helper functions (that take continuations) so I can quickly and easily generate bits and pieces of HTML from my shell. I have previously written the same helpers in JS, Python, and Ruby, but there was a certain elegance about the LISP version and that's the only version I use and maintain anymore.

I doubt anybody knows how often I'm using LISP with this little tool because they only see the resulting HTML, but it's been a big help to me.

Low traffic, but https://rl.gl is running production on SBCL (on kubernetes). Common Lisp is a joy.

Clojure direct tackles most of these problems and it seems to me (subjectively) that it's one of the most widely-used Lisps for actual production systems.

We use Clojure + ClojureScript for just about everything where I work. There are a few older applications that are in Javascript with NodeJS and we have one that is C# and .NET but the rest of the company pretty much runs on Clojure. As mentioned elsewhere, Clojure doesn't really have any of the issues that you mention.

Usually using Lisp in production means making use of either LispWorks or Allegro Common Lisp, and not the FOSS offerings.

I am using CL in pre-production to avail myself of its ability to compile & load at runtime. I haven't used Lisp in production in a while (dating back to Zetalisp!), and the decades of perspective lead me to some surprising conclusions. I have encountered neither ecosystem issues (due to quicklisp) nor community issues (due to "addition by subtraction" in the Lisp online community). However, I have encountered plenty of issues due to dependency-hell issues in the non-CL software I'm using: Python 2 vs 3 vs Python package incompatibilities; Python 2 vs 3 Ansible/Vagrant container/VM/distro incompatibilities; node.js vs npm vs inter-node-package version incompatibilities; etc. CL has been gloriously stable, and given me substantially less heartburn and fewer headaches.

Oracle used Lisp [1] in the UIs for their gen-2 cloud product. They eventually hit a wall hiring the kinds of people Oracle wanted to hire (few of whom wanted to learn an esoteric language), and made the tragic decision to move new development over to TypeScript (and port many of the key existing surfaces for ongoing maintainability). Mixed results on that. Many who were around for both the old and new code bases report that, while the old one took more effort to pick up, it was easier to trace data flow and is less prone to creating weird state bugs.

[1]: https://www.linkedin.com/pulse/building-cloud-choosing-lisp-...

I'm not a lisp programmer, but I have used emacs in the past.

For people w/ lisp dev XP, can I ask this: Is the ".emacs/config bankruptcy" issue a general problem? Specifically, when you use so many powerful devices, macros etc; but with little predictable code structure, then further development that sits well with existing code becomes pretty difficult.

Yazz Pilot (https://github.com/zubairq/pilot) was originally written in Lisp (Clojure) but we switched to Javascript, simply because it was easier to get third party developers on board with Javascript compared to Lisp

> have to restart the server every 20 days because of some memory leak

Hmm this seems like something super specific to their async setup, rather than 'common lisp leaks memory'

I just would like to add to all the great comments, that clojure also has access to the python ecosystem via libpython clj.

I've used Lisp for a production system I delivered one year ago. I used CCL as an implementation and had a lot of success.

Here i'll cover your points:

> poor ecosystem of libraries - few gems, most other half-baked

I'd say the ecosystem is high-quality. There are relatively few libraries (around 2000+) compared to other ecosystem, but on the other hand most of them are either interesting, or unique (wouldn't exist in languages that lack certain features), or really well-written. Or many of those qualities at the same time.

In the absolute sense, there are enough libraries, IMO.

If you need something that isn't available, you have at least three options:

1. Bind to a C library; for this, Common Lisp has many facilities/libs for this, some of them make this task rather easy.

2. Same as (1) but Use ECL (Embeddable Common Lisp) for integrating a C program with a Lisp program as a whole, easily calling C from Lisp and Lisp from C, etc.

3. Use the java ecosystem and use the Armed Bear Common Lisp (ABCL) implementation. This implementation makes calling java libs a piece of cake, basically you call a java method with just one line of code. Or instance a class with just one line of code, etc. Really easy.

> poor community coordination

That's a bit meaningless. There are really good quality books and resources, i think that's what counts.

> Dependency management limitations with quicklisp

Quite the opposite. Quicklisp is awesome, better than PIP or NPM. It "just works".

> And some specific red flags like:

> poor support for json[6]

The opposite, many libs for JSON. The one I use, I like a lot.

> poor support for async

What does this mean? You can use cl-async, but i wonder what would be the benefit when in CL you have actual threads and great libraries for concurrency like lparallel (which introduces parallel processing constructs) or chanL (which gives you an easy to use channel implementation).

Cl-async allows you to leverage the whole power of libuv (just like Node does), but why? I'd rather use threads.

> have to restart the server every 20 days because of some memory leak [3]

Never heard about such things.

Perhaps you are confusing the "condition - restarts system" (which is the Lisp exception handling system) with having to restart something?

> hack to tune GC [5]

The URL you cite says "We had to tune the generation sizes".

Any respecting developer who wants to release a high performance production quality service NEEDS to tune the GC. Tune the GC is not a "hack", is just configuration parameters. Ask any Java developer who has had to "tune" the JVM for best performance.

By the way, everybody raves about Golang but it has a GC system that is comparatively outdated to the ones in most Lisp implementations (or the JVM). For example CCL has a very good generational garbage collection.

> * poor ecosystem of libraries - few gems, most other half-baked

Specific to common lisp: I don't find the ecosystem to be poor but I notice that many are turned off by the look and feel of library landing pages which do feel dated. In same cases I have felt the libraries lacked documentation, like Caveman2, but in the end I found there was little to document after reading some of the source code.

Specific to Clojure: I don't think this criticism applies to Clojure at all and the popular Clojure libraries usually come with great documentation as well.

IMO, JavaScript is also littered with mounds of crappy half baked libraries as well but people still use it for server side stuff even though they have a choice to use something else.

> * poor community coordination

Which lisp community?

> * Dependency management limitations with quicklisp

What limitations? Also, if you don't like quicklisp or common lisp in general, I think Clojure really nails dependency management and find it very easy to use.

> * poor support for json[6]

Specific to CL: I can understand this because there are a number of libraries and no obvious winner. JSON isn't the only data serialization format though. Guess it depends on what you need. https://www.cliki.net/serialization

> * poor support for async

Specific to Common Lisp: There is cl-libuv: https://quickref.common-lisp.net/cl-libuv.html and wookie.

Specific to Clojure: core.async is great and if you don't like it you are also free to use node.js as your runtime with clojurescript.

> * have to restart the server every 20 days because of some memory leak [3]

If I had a dollar for every node.js production app that suffered this very same problem I could probably retire today. I thought it was interesting that the author of that article says the service was re-written in node.js given node.js is hardly immune to these sorts of problems. IMO, async is just a pain to work with and these types of issues are a manifestation of that.

> * hack to tune GC [5]

Users in JVM land also report having to resort to tuning the GC or selecting the optimal GC for their use case. I don't think this is a reason to shy away from lisp.

> If you are using lisp in production for non-trivial cases, do these issues still exist?

I have not personally encountered these issues in Clojure or CL. That is not to say they do not exist. But they also exist in plenty of other popular platforms to varying degrees. See my responses above for examples.

> and, finally, if you had to re-do your project, would you chose lisp or something else?

I would still choose lisp, either Clojure or Common Lisp. I generally favor Clojure to CL.

KDB+ is Lisp under the hood. Please count as highly successful Lisp used in production.