TADSummit online Conference, Why Erlang Matters More Than Ever in 2025, Viacheslav Katsuba

Introduction to the Erlang Session

Viacheslav Katsuba, is widely known in the Erlang community as “Ukrainian Erlanger”, active blogger and co-creator of the Hello Erlang podcast, and a contributor to discussions shaping the future of functional programming.

He is the Founder & CEO of Scalicon, a US registered software engineering company focused on Erlang/OTP development, DevOps, and backend infrastructure for mission-critical industries. Scalicon helps companies design, build, and maintain fault-tolerant distributed systems, with deep expertise in telecom, real-time messaging, fintech, and healthcare platforms.

The company provides both consulting and full-cycle development – from architecture design and legacy modernization to custom telecom protocol stacks, real-time messaging platforms, and Open Banking APIs. We’ve covered Open Banking at TADSummit over several years thanks to Miles Cheetham. Scalicon also offers team extension services, giving clients access to senior Erlang/OTP and DevOps engineers on demand.

Erlang is a programming language and runtime environment known for its built-in support for concurrency, distribution, and fault tolerance. It’s widely used in large-scale, highly concurrent systems, such as telecommunications and messaging platforms, FinTech (e.g. BNPL, Buy Now Pay Later), Healthcare (RabbitMQ is built on Erlang), and is also the foundation of the Open Telecom Platform (OTP).

OTP is a collection of libraries, tools, and design principles that enhance Erlang’s capabilities for building robust, distributed, and fault-tolerant systems. It provides ready-to-use components for common tasks, such as building web servers, databases, and messaging systems, making it easier to develop complex applications.

WhatsApp uses Erlang for its messaging servers, enabling millions of concurrent connections. Similarly, the backend for Facebook’s chat service was built using Erlang. Other implementations include Vocalink (a MasterCard company), Goldman Sachs, Nintendo, AdRoll, Grindr, BT Mobile, Samsung, OpenX, and SITA. The rise of Voice AI is a recent example of where Erlang matters today.

Erlang is an impressive global community of engineers, that needs to do more in raising industry awareness, beyond developers. Many of the Erlang implementers seem quite reluctant to discuss their use of Erlang beyond job postings. Perhaps to limit competitors copying their technology edge. So this session attempts to provide a useful resource to raise awareness across the industry. Please forward to your friends.

Introduction to Slava

I include at the end of this session a long list of links for Slava, his company Scalicon, Erlang community resources, and interesting use cases including blockchain.

Slava has been active in the Erlang community for 9 years. Erlang first appeared in 1986. It was initially developed as proprietary software within Ericsson by Joe Armstrong, Robert Virding, and Mike Williams. It was later released as free and open-source software in 1998. Therefore, as of August 2025, the Erlang language is 39 years old!

The age of the project, and Ericsson’s origin is perhaps a barrier to adoption for many web-centric developers. Assuming its a geeky telecom acronym list, with mandatory SIP (Session Initiation Protocol) knowledge. Nothing could be further from the truth.

I hope Slava and the Erlang community can convince you otherwise. From my perspective, many Voice AI companies need to get their services across most mobile phones, and Erlang is the right technology choice. It has the libraries that avoid you needing to understand SIP, and all the real time communication gotchas. We should have reached a point in 2025 where you do not need a “RTC hero” on your team, rather be part of a vibrant community, like Erlang.

Slava describes his active projects including messaging, FinTech (Buy Now Pay Later), Healthcare, and good old telecoms (he throws in some telecom acronyms and standards bodies). But do not worry, you do not need to understand diameter, unless you work in telecoms signalling.

Introduction to the Erlang Community

The core of Erlang is a mature, distributed, fault tolerant bankend that supports millions of sessions/users, with an active, friendly, and experienced community who understand fintech, messaging, healthcare, and real time communications (telecoms) etc. Most speak English as a second language.

Start here: https://erlangforums.com/ – main discussion hub for Erlang, BEAM languages, and community news. Erlang is a functional, concurrent programming language that runs on the BEAM (Bogdan’s Erlang Abstract Machine) virtual machine. The BEAM is a specialized runtime environment designed to execute Erlang bytecode efficiently, particularly for building highly concurrent, fault-tolerant, and distributed systems. That’s as deep as we go on Erlang.

Never be afraid to ask questions of the community. Check the FAQ first. If the FAQ answer does not make sense to your question, ask, and mention you checked the FAQ. This earns respect and better frames your question.

The community also operates across Github, Slack, and Reddit.

https://github.com/erlef – Foundation’s GitHub with tools, documentation, and ecosystem projects.
https://www.reddit.com/r/erlang/ – Erlang subreddit for discussions, questions, and code sharing.
https://www.linkedin.com/groups/90878/ and https://www.linkedin.com/groups/60972/ – LinkedIn Erlang groups for networking and news.

And especially if you are new to the community and you see gaps in the documentation, offer to make a documentation contribution. The community will be grateful if there’s a gap or an existing document that can be improved.

Introduction to Scalicon

Slava’s 9 years working in Erlang results in many trusted relationships with Erlang developers around the world. This means Scalicon can help you find best people for your projects and your specific regional needs.

If you need a zero downtime backend in messaging, healthcare (IoT, Internet of Things), fintech / open banking (BNPL, Buy Now Pay Later), blockchain or telecoms, Scalicon should be on your list to consider. Especially if concurrency, distributed architecture, and scale are also part of the problem.

Slava reels of a list of telecom acronyms across all the usual telecom standards. These are all built-in to Erlang, which means complex standards like SIP are natively supported without years of in-house experience and integration testing. You stand on the shoulders of giants in the Erlang community.

Within the documentation for the open source project, developers can follow recipes to implement specific capabilities, and draw on the experience of the community to implement specific features. That is keep things lightweight.

We finally defined OTP (Open Telecom Platform). It is a collection of useful middleware, libraries, and tools written in the Erlang programming language. It is an integral part of the open-source distribution of Erlang.

The name OTP was originally an acronym for Open Telecom Platform, which was a branding attempt before Ericsson released Erlang/OTP as open source. You can say Erlang and people will assume OTP is there, along with all the other libraries written over the years.

Scalicon provides the expertise to assemble what you need, beyond just Erlang. Slava gave an example of building the backend of a messaging platform, originally built in Java. Using Erlang it required only 2 people, versus the original team of 12. Plus all the APIs to access the backend remained the same, so the conversion to Erlang did not affect the ecosystem. The entire conversion was done in 2 months.

The load more than doubled, from a few hundred thousand users to five hundred thousand, running on 4 erlang servers in a cluster. This is possible given the close to 40 years of Erlang existence.

Comparing Erlang to Other Languages

Each language has their focus. Erlang is a mature, distributed, fault tolerant bankend that supports millions of sessions / users, with an active, friendly, and experienced community who understands fintech, messaging, healthcare, and real time communications (telecoms) etc.

Python, Go, Rust have their applications, Slava would not recommend Erlang for building AI infrastructure. However, when you need to connect millions of sessions / users (voice or text) to an AI service, Erlang is the answer.

Erlang Deployments

Slava gives an example of a production system, that when he got to the management console, the system had automatically recovered, and the users did not even know there was an issue. Granted the owner would have seen alarms, but baked into Erlang is mature, distributed, fault tolerant backend.

In another example, an Erlang system had a hot upgrade and all users had a non service impacting upgrade. All baked into the decades of Erlang deployments. Another example is during heavy loads more processes were spun up and the loads distributed.

Klarna (BYPL, Buy Now Pay Later) is often cited as an Erlang deployment. Its so popular I saw Hell Pizza, a New Zealand-based pizza chain, has introduced a unique ” buy now, pay later” program called “AfterLife Pay”. This program allows a select number of customers to pay for their pizza after they die, with the payment coming from their estate.

In the links section we list many deployment, a couple of examples:

Developer documentation explaining the ability to embed user-defined Erlang applications directly inside Cisco’s Network Services Orchestrator (NSO), sharing the same Erlang VM for lightweight automation and service logic. https://developer.cisco.com/docs/nso-guides-6.3/embedded-erlang-applications/
Blockchain scaling in Erlang: Code Beam Keynote with Eric Meadows-Jönsson and Ulf Wiger https://www.youtube.com/watch?v=qMKB4kjXAa4

Slava finished on Erlang is a strong choice in 2025, with many popular and modern use cases deployed today. He highlighted 5 points:

Scalability, start small at a few thousand users and grow into the millions on the same architecture
Fault tolerance. A user could misbehave, but only that user is impacted.
Built in distribution, so Erlang can deploy across on multiple servers as the load grows.
Efficient binary handling. Binaries are a fundamental data type in Erlang and are distinct from character lists (strings). So for example payments, blockchain, IoT, are handled efficiently; and
Battle tested, with a global community bringing decades of experience.

Useful Links

Erlang Community

https://erlangforums.com/ – Main discussion hub for Erlang, BEAM languages, and community news.

https://erlang.org/doc/ – Official Erlang documentation with language reference and standard library details.

https://ferd.ca/ – Blog by Fred Hebert (author of Learn You Some Erlang for Great Good!), covering Erlang, distributed systems, and operations.

https://learnyousomeerlang.com – Free online book teaching Erlang fundamentals with humor and examples.

https://medium.com/erlang-battleground – Blog with Erlang best practices, optimization tips, and architecture discussions.

https://helloerlang.github.io/ – “Hello, Erlang!” podcast exploring Erlang, Elixir, and BEAM ecosystem topics.

https://erlef.org/ – Erlang Ecosystem Foundation site with initiatives, working groups, and BEAM ecosystem promotion.

https://github.com/erlef – Foundation’s GitHub with tools, documentation, and ecosystem projects.

https://www.reddit.com/r/erlang/ – Erlang subreddit for discussions, questions, and code sharing.

https://www.linkedin.com/groups/90878/ and https://www.linkedin.com/groups/60972/ – LinkedIn Erlang groups for networking and news.

https://www.youtube.com/watch?v=M7uo5jmFDUw – Erlang in 100 Seconds — a concise video overview of the language’s strengths.

Scalicon

https://scalicon.com/ – Official Scalicon Inc. website with an overview of services, industries served, and expertise in Erlang/OTP, backend scalability, and DevOps.

https://github.com/scalicon – Scalicon’s GitHub organization, hosting open-source projects and Erlang-related code.

Slava

https://medium.com/@vkatsuba – Blog articles on Erlang/OTP, distributed systems, and fault-tolerant architectures.

https://github.com/vkatsuba – Personal GitHub profile with open-source contributions, Erlang libraries, and experiments.

https://erlangforums.com/u/vkatsuba/ – Profile on Erlang Forums, including discussions, code examples, and community advice.

https://dou.ua/users/viacheslav-katsuba/articles/ – Articles in Ukrainian about Erlang/OTP and distributed systems.

https://www.reddit.com/user/vkatsuba/ – Reddit profile with participation in Erlang and tech communities.

Some Erlang Deployments

Developer documentation explaining the ability to embed user-defined Erlang applications directly inside Cisco’s Network Services Orchestrator (NSO), sharing the same Erlang VM for lightweight automation and service logic.

Link: https://developer.cisco.com/docs/nso-guides-6.3/embedded-erlang-applications/

<Video>: Cisco ships Erlang in routers and NSO : https://www.youtube.com/watch?v=077-XJv6PLQ

A Code BEAM-style talk detailing how Cisco ships Erlang in its flagship routers and network automation tool NSO—Erlang is embedded in critical infrastructure components like ConfD and NSO.

<Video>: Erlang adoption in Cisco after Tail-F acquisition : https://www.youtube.com/watch?v=qmtpszspEaI

A conference presentation explaining how Erlang was adopted across Cisco following the acquisition of Tail-F, with examples of its role in intent-based networking and automation.

Arweave – Permanent blockchain storage with Erlang handling distributed consensus and data integrity.

GitHub: https://github.com/arweaveteam

Blog: https://arweave.medium.com/

Yellow paper: https://www.arweave.org/yellow-paper.pdf

æternity – High-performance Erlang blockchain platform with smart contracts and scalable consensus.

GitHub: https://github.com/aeternity

Blog: https://blog.aeternity.com/

Forum: https://forum.aeternity.com/

<Video> Code Beam Keynote with Eric Meadows-Jönsson and Ulf Wiger https://www.youtube.com/watch?v=qMKB4kjXAa4 (Blockchain scaling in Erlang)

<Video> Ulf Wiger – Building a Blockchain in Erlang https://www.youtube.com/watch?v=I4_xX_Zs2eE (Consensus architecture).

Zoom – XMPP-based chat backend using Erlang for millions of concurrent users.

Job post: https://www.linkedin.com/jobs/view/3341004099/?trackingId=9OsOuWvuEl4ZLZ3CA56fEQ%3D%3D&refId=d835cb91-32af-4ede-aa24-5d0b0a471e89&midToken=AQFCJJcIMTg7nA&midSig=2Kkbe8TWcIxWw1

WhatsApp – Global messaging platform running entirely on Erlang/OTP for scalability and reliability.

GitHub: https://github.com/WhatsApp

Conf: https://www.youtube.com/watch?v=R-3-WT4sB7I (Scaling WhatsApp with Erlang)
https://www.youtube.com/watch?v=lmylkEmPs-Q (Reliability at WhatsApp)
https://www.youtube.com/watch?v=LJx6mUEFAqQ (System design deep dive).

Klarna – Payment processor using Erlang for transaction reliability and concurrency.

Blogs: https://engineering.klarna.com/the-hunt-for-the-cluster-killer-erlang-bug-81dd0640aa81 (Debugging distributed bugs)
https://engineering.klarna.com/

GitHub: https://github.com/klarna

Website: https://www.klarna.com

Kivra – Digital mailbox platform in Sweden using Erlang for secure and fault-tolerant delivery.

GitHub: https://github.com/kivra

Website: https://kivra.se/sv/privat

OTP Bank ERFI – Financial services platform with Erlang components for backend operations.

GitHub: https://github.com/otp-bank

Samsung – Erlang in real-time ad bidding optimization systems (Samsung Ads).

Job post: https://jobs.nbmbaa.org/job/staff-engineer-ii-software-engineering-erlang-ad-platform-bidding-optimization-samsung-ads-mountain-view-california-884791?utm_source=chatgpt.com

RabbitMQ – Message broker built on Erlang for high-throughput, low-latency messaging.

Conf: https://www.youtube.com/watch?v=Iip0gFGsSHA (Inside RabbitMQ)
https://www.youtube.com/watch?v=k9DxUVOaz8g (Scaling messaging with Erlang)

GitHub: https://github.com/rabbitmq

Website: https://www.rabbitmq.com/

EMQX – Erlang MQTT broker for IoT, handling millions of connections efficiently.

GitHub: https://github.com/emqx

Website: https://www.emqx.com/en

Conf: https://www.youtube.com/watch?v=c285aKSjt9A (Erlang for high-throughput MQTT).