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A Tale of Scaling a Registration System

Posted on:November 11, 2022 at 10:15 AM

system top level architecture

Note: originally posted in Hebrew on facebook

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Tales of the Registration System


I, too, struggled with the registration of Burnerot Yerucham’s form last week (Nov 2022), and after we were all left feeling frustrated and disappointed with the situation, I thought to myself: “Maybe I should build a registration system for the event?“. I went to sleep, and forgot about it and carried on with my life.

So what happened?

A few days later we were sitting on the balcony at a friend’s house, the subject of the ticketing situation of Burnerot’s Yerucham came up in the conversation, and I had the feeling of “Fuck it, this is happening right now”. So I took my laptop out (at midnight 😅) and within an hour had a working prototype. As appropriate to my mad frontend skillz, it took me more time to center some divs than building the whole “registration system” backend.

The next day - did some finishing touches, and sent a message to two friends asking them to connect me to the event organizers.

“Yo! I built this cute mini-project last night, it should handle any load that comes… If it looks like it can help with the registration tomorrow, talk to me”.

We talked, did some ping-pong over the contents and fields of the page, and… voilà, suddenly there’s a functioning and live registration system.


Up until now, I didn’t suspect a thing, and then I got a message:

“Say, do you think you can also help with the sale of Park Yarden today?”

We’re going for it!

17:00 - I duplicate the project, upload a first version of Park Yarden to the air

* Tweaking, talking, tweaking, talking *

[We changed some content and the captcha, detailed explanation here on why some people saw an old version of the image]

* Tweaking, talking, tweaking, talking *

20:00 - The registration starts

Confused burners arrive to the shiny webpage, but there aren’t a lot of registrations.

* First post about captcha problem *

(“Hmm… Looks like I know what the problem is, I’ll push a fix real quick”)

The fix is now live, people register, and form closed at 20:30

After analyzing the situation, the organizers drew conclusions and decided that due to the Captcha issue, another registration round will be made in order to give everyone a fair chance.

The Meme Department receives new material, everyone is considered a robot, exposed as a Cylon, the operation succeeded but the patient died.

(Memes Department, love you guys ❤️)

And there was evening, and there was morning—the fifth day (aka Thursday)

There are 2 sales, Park Yarden at 19:00, Park Yerucham at 20, this time everything is up running from the get go, and everyone is relaxed.

19:00 - Park Yarden - The registration begins

We’re seeing reports of DNS issues for a (presumably) small part of the people

Me: “Damn, 🤦‍♀️, it’s always DNS” (Sorry Roy, hope to see you in Park Yerucham)

It's always DNS

20:00 Yerucham registration - everything is flowing

20:01 The Memes Department is in a moment of silence

20:13 name redacted marked safe from Burnerot Sale

It was fun raising this whole system, and I hope you weren’t too disappointed that it didn’t crash completely 😉

Under The Hood - Technical Details

What happened with the captcha??

So, cloudflare has an awesome system in general, but part of how they stand the load of thousands of people pounding on the same website at the same time, is by memorizing (caching) which content to serve on the site.

For example, instead of looking up which image is stored behind the url, we can assume this file does not change over short periods of time, and keep a copy in memory to serve instead of loading it from disk every time. This approach failes when the content changes on disk, and the cache is not invalidated.

At 7:30 pm on Wednesday, I updated the image, and uploaded an updated version of the Park Yarden form, the name of the infamous file was fake_captcha.png (this real captcha system, but an improvisation that was done less than a day before the sale)

I have changed content of the image and not the filename, As consequence, some people received an older version of the file with this name.

(By the way, this is a totally cloudflare bug that it’s even possible that this happens, and I intend to open a complaint against them to fix this) The fix was to change the filename to something like fake_captcha1.png

How did the “registration system” band look like?

I used Google Cloud Functions, the setup was quick and easy, and the actual usage was within the free tier.

The important part here is: Google’s logging system support enormous amounts of data, we didn’t even scratch the limits of this system.

My “smart” function included less than 30 lines of code, it recorded at what exact time the registration was made, and in the end I just called to print, that’s it.

These prints are stored in Google’s logs, and after closing the form I exported the contents to a spreadsheet, and transferred the data to the organizers and told them to sort the content by the time signature of the entries, and my work here is done.

I hope you enjoyed this story

it was fun registering y’all 💜💜