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0x70dd | 9 months ago | on: Conformance checking at MongoDB: Testing that our code matches our TLA+ specs

Until very recently, at the company I work for, we were running one of the largest (if not the largest) replica set cluster in terms of number of documents stored (~20B) and data size ~11TB. The database held up nicely in the past 10 years since the very first inception of the product. We had to do some optimizations over the years, but those are expected with any database. Since Mongo Atlas has a hard limit on the maximum disk size of 14TB we explored multiple migration options - sharding Mongo or moving to Postgres/TimescaleDB or another time series database. During the evaluation of alternative database we couldn't find one which supported our use case, that's highly available, could scale horizontally and that's easily maintainable (e.g. upgrades on Mongo Atlas require no manual intervention and there's no downtime even when going to the next major version). We had to work around numerous bugs that we encountered during sharding that were specific to our workloads, but the migration was seamless and required ~1h of downtime (mainly required to fine-tune database parameters). We've had very few issues with it over the years. I think Mongo is a mature technology and it makes sense depending on the type of data you're storing. I know at least few other healthcare companies that are using it for storing life-critical data even at a larger scale.

0x70dd | 1 year ago | on: Record 4 Camera Angles at Once Using Only iPhones and iPads

iPhones record videos with variable frame rate, which makes them unsuitable for syncing the video with a separate recorded audio track (e.g. when recording guitars). The video and audio would ever so slightly go our of sync. I wish there was a way to use fixed frame rate when recording.

0x70dd | 1 year ago | on: Ointment containing DNA molecules can combat allergic contact dermatitis

I have a severe form of allergic dermatitis that I've been trying to get under control for close to 10 years now. At one point to it so bad I couldn't take a shower without being in excruciating pain, I couldn't sleep, I could barely go through the day. The problem with all of the existing treatments, including the latest generation of monoclonal antibodies and JAK inhibitors is that they downregulate your immune system and they make you more sensitive to allergens if you discontinue the treatment. The only thing that made me better over time was stopping all drugs (including topical ones). It got worse for close to a year, but in 2-3 years my skin "healed". I'm still allergic and do get rashes occasionally, but I'm way less sensitive now.

0x70dd | 4 years ago | on: Wavelets allow researchers to transform and understand data

Wavelets are used for pattern recognition in many iris recognition systems. First, the position of the iris in the input image is determined, then any eyelash and eyelid occlusions are removed and the iris is extracted by converting it to a polar coordinated image. The resulting image signal is convolved with wavelets of different shapes and sizes. The resulting signal is encoded using phase demodulation to produce an IrisCode. Two iris codes can be checked for a match by computing their hamming distance. [1] is the paper which describes the original system invented by Daugman. [2] is an open source implementation of that method.

[1] https://www.robots.ox.ac.uk/~az/lectures/est/iris.pdf [2] http://iris.giannaros.org/

0x70dd | 5 years ago | on: Differential Datalog

Rego, the language used in Open Policy Agent, is based on and extends Datalog. It's gaining a lot of traction in the past couple of years for evaluating authorization policies.

0x70dd | 6 years ago | on: Climate Change Is Killing Alpine Skiing as We Know It

I wouldn't call it healthier due to the risk of avalanches and in my experience it's not negligible. It requires some complex skills of being able to both judge the terrain and act fast if something happens. And even then, accidents happen. How many people die annually on the slopes of ski resorts and how many die in avalanches while skiing?

0x70dd | 6 years ago | on: How to Exit Vim

Every time I open vim by accident, I have to restart my computer.

0x70dd | 6 years ago | on: The pointlessness of daily standups

I had the exact same feeling when we started having daily standups about 4 years ago for a green field project. Now that most of the original developers are no longer in the company I feel glad that I actually paid attention. It turns out that I have a very good knowledge about how and what every micro-service in our stack does. What's discussed in those standups might not be relevant for day-to-day work, but on a higher level it can help developers understand the architecture of a complex system better.

0x70dd | 6 years ago | on: Get Started Making Music

Recently I switched to Ardour for recording guitars on Linux - it has great VST support, allows syncing music with videos, and has automation built-in. Even Amplitube works through LinVst.

I was also blown away by their pricing - you can pay as little as $1 for the full version, which is what I did, but after seeing how well it works, I did a donation to match the recommended price of $45.

0x70dd | 6 years ago | on: San Francisco Becomes First U.S. City to Pass an E-Cigarette Ban

Almost 2 years ago I saw a comment on HN from a guy who quit smoking after reading Alan Carr's "The Easy Way". As a person who was heavily addicted, often smoking more than a pack a day, struggling to quit for good, I decided to read the book. It did wonders - for almost 2 years I haven't smoked and I don't miss it. It also helped friends to whom I recommended the book. I wanted to drop a comment here in case I can inspire others to give it a try.
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