Thinking of the person who pressed Go on today’s Crowdstrike release
20 Jul2024

Today’s tweet about the Crowdstrike incident, which seemingly brought the modern IT world to a standstill, reminded me of the darkest day of my professional life — when I accidentally knocked out internet access in a city of over 200,000 people.

It was my second year of university and I worked for a the largest local ISP in my home city as a junior system administrator. We had a large wireless network (~100km in diameter) covering our whole city and many surrounding rural areas. This network was used by all major commercial banks and many large enterprises in the area (bank branches, large factories, radio stations, etc).

To cover such a large area (in Ukraine in early 2000s), about 50% of which were rural villages and towns, we basically had to build a huge wifi network, that had a very powerful antenna in the center and many smaller regional points of presence would connect to it using directional wifi antennas and then distribute the traffic locally. The core router connected to the central antenna was located at the top floor of the highest building in the area about 20 min away from our office.

One day I was working on some monitoring scripts for the central router (which was basically a custom-built FreeBSD server). I’d run those scripts on a local stand I had on my table, make some changes, run it again, etc. We did not have VMs back then, so experimental work would happen on real hardware that was a clone of a production box. In the middle of my local debugging, I received a monitoring alert from our production saying that our core router had some (non-critical) issues. Since I was on-call that day, I decided take a look. Fixing the issue on the router, I went back to my debugging and successfully finished the job after about an hour.

And that’s where things went wrong… When I wanted to shut down my local machine, I switched to a terminal that was connected to the box, typed “poweroff”, pressed Enter… and only then realized that I did it on a wrong server! 🤦🏻‍♂️ I had that second terminal window opened ever since the monitoring alert an hour ago, and now I ended up shutting down the core router for our whole city-wide network!

What’s cool is that there was no blame in the aftermath of the incident. The team understood the mistake and focused on fixing the problem. We ended up having to drive to the central station and manually power the router back on. Back then we did not have any remote power management set up for that server and IPMI did not exist back then. Dark times indeed! 😉

As a result of that mistake, our whole city’s banking infrastructure and a bunch of other important services were down for ~30 minutes. Following the incident, we have made a number of improvements to our infrastructure and our processes (I don’t remember the details now) making the system a lot more resilient to similar errors.

Looking back now, huge kudos to my bosses for not firing me back then! This incident profoundly influenced my career in many ways:

First, the thrill of managing such vast infrastructures made me want to stay in technical operations rather than shifting to pure software development, a path many of my peers chose at the time. Then, having experienced such a massive error firsthand, I’ve always done my absolute best to safeguard my systems against failures, optimizing for quick recovery and being paranoid about backups and redundancy. Finally, it was a pivotal moment in my understanding of the value of blameless incident process long before the emergence of the modern blameless DevOps and SRE cultures — a management lesson that has deeply informed my approach to leadership and system design ever since.

Interview: Inside Shopify’s Modular Monolith
16 Jun2024

This is my interview with Dr. Milan Milanovic originally published on his newsletter Tech World With Milan where we discussed Shopify  architecture, tech stack, testing, culture, and more.

1.  Who is Oleksiy?

I have spent most of my career in technical operations (system administration, later called DevOps, nowadays encompassed by platform engineering and SRE disciplines). Along the way, I worked at Percona as a MySQL performance consultant and then operated some of the largest Ruby on Rails applications in the world, all the while following the incredible story of Shopify’s development and growth.

Finally, after decades of work in operations, when a startup I was at got acquired by Elastic, I decided to move into software engineering. After 5 years there, I needed a bigger challenge, which felt like the right moment to join Shopify.

I started with the Storefronts group (the team responsible for Storefront themes, all the related infrastructure, and the Storefront rendering infrastructure) at Shopify at the beginning of 2022. Two years later, I can confidently say that Shopify’s culture is unique. I enjoy working with the team here due to the incredible talent density I have never encountered. Every day, I am humbled by the caliber of people I can work with and the level of problems I get to solve.

2.  What is the role of the Principal Engineer at Shopify?

Before joining Shopify, I was excited about all the possibilities associated with the Principal Engineer role. Immediately, I was surprised at how diverse the Principal Engineering discipline was at the company. We have a range of engineers here, from extremely deep and narrow experts to amazing architects coordinating challenging projects across the company. Even more impressive is that you have a lot of agency in the shape of a Principal Engineer you will be, provided that the work aligns with the overarching mission of making commerce better for everyone. After 2 years with the company, I found myself in a sweet spot of spending ~75% of my time doing deep technical work across multiple areas of Storefronts infrastructure, and the rest is spent on project leadership, coordination, etc.

3.  The recent tweet by Shopify Engineering shows impressive results achieved by your system. What is Shopify’s overall architecture?

The infrastructure at Shopify was one of the most surprising parts of the company for me. I have spent my whole career building large, heavily loaded systems based on Ruby on Rails. Joining Shopify and knowing upfront a lot about the amount of traffic they handled during Black Friday, Cyber Monday (BFCM), and flash sales, I was half-expecting to find some magic sauce inside. But the reality turned out to be very different: the team here is extremely pragmatic when building anything. It comes from Shopify’s Founder and CEO Tobi Lütke himself: if something can be made simpler, we try to make it so. As a result, the whole system behind those impressive numbers is built on top of fairly common components: Ruby, Rails, MySQL/Vitess, Memcached/Redis, Kafka, Elasticsearch, etc., scaled horizontally.

Shopify Engineering Tweet about the amount of traffic they handled during Black Friday

What makes Shopify unique is the level of mastery the teams have built around those key components: we employ Ruby core contributors (who keep making Ruby faster), Rails core contributors (improving Rails), MySQL experts (who know how to operate MySQL at scale), and we contribute to and maintain all kinds of open-source projects that support our infrastructure. As a result, even the simplest components in our infrastructure tend to be deployed, managed, and scaled exceptionally well, leading to a system that can scale to many orders of magnitude over the baseline capacity and still perform well.

4.  What is Shopify’s tech stack?

Given that databases (and stateful systems in general) are the most complex components to scale, we focus our scaling on MySQL first. All shops on the platform are split into groups, each hosted on a dedicated set of database servers called a pod. Each pod is wholly isolated from the rest of the database infrastructure, limiting the blast radius of most database-related incidents to a relatively small group of shops. Some more prominent merchants get their dedicated pods that guarantee complete resource isolation.

Over the past year, some applications started relying on Vitess to help with the horizontal sharding of their data.

On top of the database layer is a reasonably standard Ruby on Rails stack: Ruby and Rails applications running on Puma, using Memcached for ephemeral storage needs and Elasticsearch for full-text search. Nginx + Lua is used for sophisticated tasks, from smart routing across multiple regions to rate limiting, abuse protection, etc.

This runs on top of Kubernetes hosted on Google Cloud in many regions worldwide, making the infrastructure extremely scalable and responsive to wild traffic fluctuations.

Check the full Shopify tech stack at Stackshare.

A Pods Architecture To Allow Shopify To Scale (Source: Shopify Engineering)

What are Pods exactly?

The idea behind pods at Shopify is to split all of our data into a set of completely independent database (MySQL) clusters using shop_id as the sharding key to ensure resource isolation between different tenants and localize the impact of a “noisy neighbor” problem across the platform. 

Only the databases are podded since they are the hardest component to scale. Everything else that is stateless is scaled automatically according to the incoming traffic levels and other load parameters using a custom Kubernetes autoscale.

5. Is the monolith going to be broken into microservices?

Shopify fully embraces the idea of a Majestic Monolith—most user-facing functionality people tend to associate with the company is served by a single large Ruby on Rails application called “Shopify Core.” Internally, the monolith is split into multiple components focused on different business domains. Many custom (later open-sourced) machinery have been built to enforce coding standards, API boundaries between components, etc.

The rendering application behind all Shopify storefronts is completely separate from the monolith. This was one of the cases where it made perfect sense to split functionality from Core because it is relatively simple. Load data from a database, render Liquid code, and send the HTML back to the user – the absolute majority of requests it handles. Given the amount of traffic on this application, even a small improvement in its efficiency results in enormous resource savings. So, when it was initially built, the team set several strict constraints on how the code is written, what features of Ruby we prefer to avoid, how we deal with memory usage, etc. This allowed us to build a pretty efficient application in a language we love while carefully controlling memory allocation and the resources we spend rendering storefronts.

Shopify application components

In parallel with this effort, the Ruby infrastructure team (working on YJIT, among other things) has made the language significantly faster with each release. Finally, in the last year, we started rewriting parts of this application in Rust to improve efficiency further.

Answering your question about the future of the monolith, I think outside of a few other localized cases, most of the functionality of the Shopify platform will probably be handled by the Core monolith for a long time, given how well it has worked for us so far using relatively standard horizontal scalability techniques.

6. How do you do testing?

Our testing infrastructure is a multi-layered set of checks that allows us to deploy hundreds of times daily while keeping the platform safe. It starts with a set of tests on each application: your typical unit/integration tests, etc. Those are required for a change to propagate into a deployment pipeline (based on the Shipit engine, created by Shopify and open-sourced years ago.

Shopify overall infrastructure

During the deployment, a very important step is canary testing: a change will be deployed onto a small subset of production instances, and automation will monitor a set of key health metrics for the platform. If any metrics move in the wrong direction, the change is automatically reverted and removed from production immediately, allowing developers to figure out what went wrong and try again when they fix the problem. Only after testing a change on canaries for some time the deployment pipeline performs a full deployment. The same approach is used for significant schema changes, etc.

7. How do you do deployments?

All Shopify deployments are based on Kubernetes (running on GCP), so each application is a container (or a fleet of containers) somewhere in one of our clusters. Our deployment pipeline is built on the Shipit engine (created by Shopify and open-sourced years ago). Deployment pipelines can get pretty complex, but it mostly boils down to building an image, deploying it to canaries, waiting to ensure things are healthy, and gradually rolling out the change wider across the global fleet of Kubernetes clusters.

Shipit also maintains the deployment queue and merges multiple pull requests into a single deployment to increase the pipeline’s throughput.

Shipit open-source deployment tool by Shopify (Source)

8. How do you handle failures in the system? 

The whole system is built with many redundancy and horizontal auto-scaling (if possible), which helps prevent large-scale outages. But there are always big and small fires to handle. So, we have a dedicated site reliability team responsible for keeping the platform healthy in the face of constant change and adversarial problems like bots and DDoS attacks. They have built many automated tools to help us handle traffic flashes and, if needed, degrade gracefully. Some interesting examples: they have automated traffic analysis tools helping them scope ongoing incidents down to specific pods, shops, page types, or traffic sources; then the team can control the flow of traffic by pod or shop, re-route traffic between regions, block or slow down requests from specific parts of the world, prioritize particular types of traffic and apply anti-adversarial measures across our network to mitigate attacks.

Finally, each application has an owner team (or a set of teams) that can be paged if their application gets unhealthy. They help troubleshoot and resolve incidents around the clock (being a distributed company helps a lot here since we have people across many time zones).

9. What challenges are you working on right now in your team?

We have just finished a large project to increase the global footprint of our Storefront rendering infrastructure, rolling out new regions in Europe, Asia, Australia, and North America. The project required coordination across many different teams (from networking to databases to operations, etc.) and involved building completely new tools for filtered database replication (since we cannot replicate all of our data into all regions due to cost and data residency requirements), making changes in the application itself to allow for rendering without having access to all data, etc. This large effort has reduced latency for our buyers worldwide and made their shopping experiences smoother.

Next on our radar are further improvements in Liquid rendering performance, database access optimization, and other performance-related work.

Farewell to Elastic and The New Chapter
23 Feb2022

Today was my last day at Elastic. After 4.5 years with the company and almost 9 years with the Swiftype (and later Enterprise Search) team, I have decided to move on and see what else is out there. I wanted to use this post to clarify the reasoning behind the decision because a lot of people have been reaching out over the past month wondering about the details.

For most of my career (for at least 15-17 years before joining Elastic) I have worked in small to medium-sized startups, always in SaaS, moving really fast and having my impact on the business be mostly tied to my ability to ship. I loved that, even though it was often painful and stressful. My brain ended up being trained to derive dopamine from the constant feeling of shipping, constant feeling of overcoming challenges and solving problems.

Then, we got acquired by Elastic – a truly amazing company, honestly, the best company I have ever worked for and, unfortunately, a company that ships packaged software with its inherent effects on development process. At first, while my projects revolved around security and compliance, then around internal code migrations, integration into the Elastic ecosystem, etc, I felt really happy – I would do the really challenging work and derive pleasure from overcoming those challenges.

Unfortunately, over time the initial rush of excitement faded away and I have realized, that the most challenging problems within our product have been solved and I ended up in a position of working on a packaged product, building features with a release cycle of 6-8 weeks. The product is amazing, the features are really exciting, but the very long feedback cycle simply did not work for me after so many years in SaaS.

I still believe in Elastic, I love the company, the team and the amazing culture we have built over the years. But I need to ship faster, move faster, get feedback from my users sooner. After considering different options, I have decided to join Shopify – a large and fast moving Rails-based company, where I hope to get a chance to once again experience the thrill of fast delivery and tight feedback loops. Let’s see how it goes 🙂

Edge Web Server Testing at Swiftype
28 Apr2018

This article has been originally posted on Swiftype Engineering blog.

For any modern technology company, a comprehensive application test suite is an absolute necessity. Automated testing suites allow developers to move faster while avoiding any loss of code quality or system stability. Software development has seen great benefit come from the adoption of automated testing frameworks and methodologies, however, the culture of automated testing has neglected one key area of modern web application serving stack: web application edge routing and multiplexing rulesets.

From modern load balancer appliances that allow for TCL based rule sets; local or remotely hosted varnish VCL rules; or in the power and flexibility that Nginx and OpenResty make available through LUA, edge routing rulesets have become a vital part of application serving controls.

Over the past decade or so, it has become possible to incorporate more and more logic into edge web server infrastructures. Almost every modern web server has support for scripting, enabling developers to make their edge servers smarter than ever before. Unfortunately, the application logic configured within web servers is often much harder to test than that hosted directly in application code, and thus too often software teams resort to manual testing, or worse, customers as testers, by shipping their changes to production without edge routing testing having been performed.

In this post, I would like to explain the approach Swiftype has taken to ensure that our test suites account for our use of complex edge web server logic
to manage our production traffic flow, and thus that we can confidently deploy changes to our application infrastructure with little or no risk.

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Compliance-Driven Development or the Story Behind Swiftype’s SOC2 Certification
18 Jan2018
Based on my experience, just a decade ago not many people within the Silicon Valley startup community considered compliance an important stepping stone in a company’s development roadmap. And when it came to compliance for startups, it was nearly synonymous with PCI/DSS — mandatory certification used by the credit card industry. Over the last few years though, the rise in the number of startups working with large amounts of private and confidential data (fintech, healthcare, etc) and subsequently the rise in the magnitude of data breaches, led our industry to accept the idea that compliance and certifications are not just for the “big guys”. Nowadays, even very small companies are pressed to go through formal certifications if they want people to trust them with private or confidential data.

That is exactly what happened to Swiftype at the beginning of 2017. While preparing for a public release of our latest product (Swiftype Enterprise Search), we understood that it was going to involve a lot of confidential information and we would need to be able to assure our customers of our capabilities to protect their data. In addition to the marketing aspect, there was a security angle to the problem as well: we were looking for a standard framework that could be used by our small team to ensure the safety of customer data, guiding us through the process. Based on those considerations, we decided to go through a formal SOC 2 certification. In this article, I will describe our journey towards the certification and our findings along the way.


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