Docker キャプテンは、開発者コミュニティのリーダーであり、それぞれの分野の専門家であり、Docker の知識を他の人と共有することに情熱を注いでいます。「From the Captain's Chair」は、あるキャプテンを詳しく見て、彼らとその経験について詳しく知るブログシリーズです。
Today we are interviewing Igor Aleksandrov. Igor is the CTO and co-founder of JetRockets, a Ruby on Rails development agency based in NYC, bringing over 20 years of software engineering experience and a deep commitment to the Rails ecosystem since 2008. He’s an open-source contributor to projects like the Crystal programming language and Kamal, a regular conference speaker sharing expertise on different topics from container orchestration to migration from React to Hotwire.
Can you share how you first got involved with Docker? What inspired you to become a Docker Captain?
Looking back at my journey to becoming a Docker Captain, it all started with a very practical problem that many Rails teams face: dependency hell.
By 2018, JetRockets had been building Ruby on Rails applications for years. I’d been working with Rails since version 2.2 back in 2009, and we had established solid development practices. But as our team grew and our projects became more complex, we kept running into the same frustrating issues:
- “It works on my machine” became an all-too-common phrase during deployments
- Setting up new developer environments was a time-consuming process fraught with version mismatches
- Our staging and production environments occasionally behaved differently despite our best efforts
- Managing system-level dependencies across different projects was becoming increasingly complex
We needed a unified way to manage application dependencies that would work consistently across development, staging, and production environments.
Unlike many teams that start with Docker locally and gradually move to production, we decided to implement Docker in production and staging first. This might sound risky, but it aligned perfectly with our goal of achieving true environment parity.
We chose our first Rails application to containerize and started writing our first Dockerfile. Those early Dockerfiles were much simpler than the highly optimized ones we create today, but they solved our core problem: every environment now ran the same container with the same dependencies.
Even though AWS Beanstalk has never been a developer friendly solution, the goal was reached – we had achieved true environment consistency, and the mental overhead of managing different configurations across environments had virtually disappeared.
That initial Docker adoption in 2018 sparked a journey that would eventually lead to me becoming a Docker Captain. What began with a simple need for dependency management evolved into deep expertise in container optimization, advanced deployment strategies with tools like Kamal, and ultimately contributing back to the Docker community.
Today, I write extensively about Rails containerization best practices, from image slimming techniques to sophisticated CI/CD pipelines. But it all traces back to that moment in 2019 when we decided to solve our dependency challenges with Docker.
来年の個人的な目標は何ですか?
I want to speak at more conferences and meetups, sharing the expertise I’ve built over the years. Living in the Atlanta area, I would like to become more integrated into the local tech community. Atlanta has such a vibrant IT scene, and I think there’s a real opportunity to contribute here. Whether that’s organizing Docker meetups, participating in Rails groups, or just connecting with other CTOs and technical leaders who are facing similar challenges.
もしあなたがテクノロジー業界で働いていたら、代わりに何をしていましたか?
If I weren’t working in tech, I think I’d be doing woodworking. There’s something deeply satisfying about creating things with your hands, and woodworking offers that same creative problem-solving that draws me to programming – except you’re working with natural materials and traditional tools instead of code.
I truly enjoy working with my hands and seeing tangible results from my efforts. In many ways, building software and building furniture aren’t that different – you’re taking raw materials, applying craftsmanship and attention to detail, and creating something functional and beautiful.
If not woodworking, I’d probably pursue diving. I’m already a PADI certified rescue diver, and I truly like the ocean. There’s something about the underwater world that’s entirely different from our digital lives – it’s peaceful, challenging, and always surprising. Getting my diving instructor certification and helping others discover that underwater world would be incredibly rewarding.
Dockerコミュニティとのコラボレーションで思い出に残るストーリーを共有できますか?
One of the most rewarding aspects of being a Docker Captain is our regular Captains meetings, and honestly, I enjoy each one of them. These aren’t just typical corporate meetings – they’re genuine collaborations with some of the most passionate and knowledgeable people in the containerization space.
What makes these meetings special is the diversity of perspectives. You have Captains from completely different backgrounds – some focused on enterprise Kubernetes deployments, others working on AI, developers like me optimizing Rails applications, and people solving problems I’ve never even thought about.
現在お気に入りのDocker製品や機能は何ですか、そしてその理由は何ですか?
Currently, I’m really excited about the Build Debugging feature that was recently integrated into VS Code. As someone who spends a lot of time optimizing Rails Dockerfiles and writing about containerization best practices, this feature has been a game-changer for my development workflow.
When you’re crafting complex multi-stage builds for Rails applications – especially when you’re trying to optimize image size, manage build caches, and handle dependencies like Node.js and Ruby gems – debugging build failures used to be a real pain.
最近解決したトリッキーな技術的課題について教えていただけますか?
Recently, I was facing a really frustrating development workflow issue that I think many Rails developers can relate to. We had a large database dump file, about 150GB, that we needed to use as a template for local development. The problem was that restoring this SQL dump into PostgreSQL was taking up to an hour every time we needed to reset our development database to a clean state.
For a development team, this was killing our productivity. Every time someone had to test a migration rollback, debug data-specific issues, or just start fresh, they’d have to wait an hour for the database restore. That’s completely unacceptable.
Initially, we were doing what most teams do: running pg_restore against the SQL dump file directly. But with a 150GB database, this involves PostgreSQL parsing the entire dump, executing thousands of INSERT statements, rebuilding indexes, and updating table statistics. It’s inherently slow because the database engine has to do real work.
I realized the bottleneck wasn’t the data itself – it was the database restoration process. So I wrote a Bash script that takes an entirely different approach:
- Create a template volume: Start with a fresh Docker volume and spin up a PostgreSQL container
- One-time restoration: Restore the SQL dump into this template database (this still takes an hour, but only once)
- Volume snapshot: Use a BusyBox container to copy the entire database volume at the filesystem level
- Instant resets: When developers need a fresh database, just copy the template volume to a new working volume
The magic is in step 4. Instead of restoring from SQL, we’re essentially copying files at the Docker volume level. This takes seconds instead of an hour because we’re just copying the already-processed PostgreSQL data files.
Docker volumes are just filesystem directories under the hood. PostgreSQL stores its data in a very specific directory structure with data files, indexes, and metadata. By copying the entire volume, we’re getting a perfect snapshot of the database in its “ready to use” state.
The script handles all the orchestration – creating volumes, managing container lifecycles, and ensuring the copied database starts up cleanly. What used to be a one-hour reset cycle is now literally 5-10 seconds. Developers can experiment freely, test destructive operations, and reset their environment without hesitation. It’s transformed how our team approaches database-dependent development.
すべての開発者に知っておいてほしいDockerのヒントは何ですか?
If something looks weird in your Dockerfile, you are doing it wrong. This is the single most important lesson I’ve learned from years of optimizing Rails Dockerfiles. I see this constantly when reviewing other developers’ container setups – there’s some convoluted RUN command, a bizarre COPY pattern, or a workaround that just feels off.
Your Dockerfile should read like clean, logical instructions. If you find yourself writing something like:
RUN apt-get update && apt-get install -y wget && \
wget some-random-script.sh && chmod +x some-random-script.sh && \
./some-random-script.sh && rm some-random-script.sh
…you’re probably doing it wrong.
The best Dockerfiles are almost boring in their simplicity and clarity. Every line should have a clear purpose, and the overall flow should make sense to anyone reading it. If you’re adding odd hacks, unusual file permissions, or complex shell gymnastics, step back and ask why.
This principle has saved me countless hours of debugging. Instead of trying to make unusual things work, I’ve learned to redesign the approach. Usually, there’s a cleaner, more standard way to achieve what you’re trying to do.
実生活で非技術的なオブジェクトをコンテナ化できるとしたら、それは何でしょうか、そしてその理由は何ですか?
If I could containerize any non-technical object, it would definitely be knowledge itself. Imagine being able to package up skills, experiences, and expertise into portable containers that you could load and unload from your mind as needed. As someone who’s constantly learning new technologies and teaching others, I’m fascinated by how we acquire and transfer knowledge. Currently, if I want to dive deep into a new programming language like I did with Crystal, or master a deployment tool like Kamal, it takes months of dedicated study and practice.
But what if knowledge worked like Docker containers? You could have a “Ruby 3.3 expertise” container, a “Advanced Kubernetes” container, or even a “Woodworking joinery techniques” container. Need to debug a complex Rails application? Load the container. Working on a diving certification course? Swap in the marine biology knowledge base.
The real power would be in the consistency and portability – just like how Docker containers ensure your application runs the same way everywhere, knowledge containers would give you the same depth of understanding regardless of context. No more forgetting syntax, no more struggling to recall that one debugging technique you learned years ago.
Plus, imagine the collaborative possibilities. Experienced developers could literally package their hard-earned expertise and share it with the community. It would democratize learning in the same way Docker democratized deployment.
Of course, the human experience of learning and growing would be lost, but from a pure efficiency standpoint? That would be incredible.
Where can people find you online? (talks, blog posts, or open source projects, etc)
I am always active in X (@igor_alexandrov) and on LinkedIn. I try to give at least 2-3 talks at tech conferences and meetups each year, and besides this, I have my personal blog.
ラピッドファイアの質問
猫か犬か?
イヌ
朝型人間か夜型人間か?
両
好きなホッとする食べ物は?
餃子
友人があなたを表す言葉を一言で表現しますか?
Perfectionist
最近始めた趣味は?
サイクリング
