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Even using your numbers, if you want to keep say only 3 months of data, we're talking about 1-2 PB already. Being able to query those data across different segm

by cdavid 4y ago

Even using your numbers, if you want to keep say only 3 months of data, we're talking about 1-2 PB already. Being able to query those data across different segments, aggregate into different dimensions is already quite far beyond what you can do w/ off the shelve postgresql or sqlite. And in general, in companies the size of airbnb, you don't control all the data sources to be super efficient, because that's organizationally impossible. So instead the data will be de normalized, etc. There is a reason most companies with those problems use systems like BQ, snowflake, and co. If it were possible to do with sqlite, a lot of them would do it.

Dylan16807 4y ago
> Even using your numbers, if you want to keep say only 3 months of data, we're talking about 1-2 PB already. Am I doing the math wrong? "1 billion" was supposed to be lifetime stays, but let's say it's per year. Here's the math using 'my' numbers: 1 billion stays per year * 100 searches per stay * 150 bytes per search = 15TB per year 1 billion stays per year * 1000 page loads per stay * 15 bytes per page load = 15TB per year How are you getting petabytes? If 3 months is 1-2 hundred million stays, you'd need to store ten million bytes per stay to reach 1-2PB. (And images don't count, they wouldn't be in the database.)
- cdavid 4y ago
  > Am I doing the math wrong? Your mistake is to assume you need to look at per stay. You should look at per query if you want to improve your search. My math is based on the following: - 1000 qps - 1 query has on average 100 results - for each query you want to at least get the query string, the list of document ids, and the interaction for each document (view/click/etc.). So we're talking 1e3 (qps) * ~1e5 (seconds per day) * 1e2 = 10 billions events a day -> 1 peta events for 3 months. Even assuming 1 byte per event, and 1000 qps being super conservative for airbnb I suspect.
  - Dylan16807 4y ago
    Your math is similar to mine, but you mixed up "tera" and "peta". 1000 billion events is 1 tera-event, and 0.001 peta-events.
    - cdavid 4y ago
      you're right about TB vs PB ofc :) But then keep in mind the assumptions were super conservative: * 1qps is likely off by at least half order magnitude * 1 byte per even is obviously off by several order of magnitudes, let's say just 1.5 order of magnitude. You need to know if an even is click/buy/view/..., you need the doc id that will likely be a 16 bytes uuid, etc. * etc. So you will reach the PB if not per a few month, but at least per year. sqlite or "simple" postgres really is not gonna cut it. I work in search for a C2C marketplace that is smaller than airbnb, and w/o going into details, we reach those orders of magnitude in big query.
      - Dylan16807 4y ago
        Okay, if you're going to try to inflate your estimate by 200x so you can get back to petabyte range then I'll do a more detailed comparison. > * 1qps is likely off by at least half order magnitude Wasn't your math based on a thousand queries per second? I don't think that's unreasonably small. And my math, in the "let's say it's 1 billion stays per year" version, assumes three thousand queries per second. And then you're assuming 100 clicks per query, a hundred thousand page loads per second. And I'm assuming 10 clicks per query, thirty thousand page loads per second. Are those numbers way too small? > * 1 byte per even is obviously off by several order of magnitudes, let's say just 1.5 order of magnitude. You need to know if an even is click/buy/view/..., you need the doc id that will likely be a 16 bytes uuid, etc. Sure, I think 30 bytes is reasonable for a click. When I said 15 I was squeezing a bit much. But timestamp, session ID, page template ID, property/comment/whatever ID, page number, click/buy/view byte if that isn't implied by page template... no need for that be more than 30 bytes total. 30 bytes per event * 30000 events per second * 1 year = only 2 hard drives worth of click data. And historically their stays were significantly less than they are today. > I work in search for a C2C marketplace that is smaller than airbnb, and w/o going into details, we reach those orders of magnitude in big query. Well there's a lot of factors here. Maybe your search results are a lot more complicated than "25-50 properties at a time". Maybe you're tracking more data than just clicks. Maybe you have very highly used pages that need hundreds of bytes of data to render. Maybe you're using UUIDs when much smaller IDs would work. Maybe you're storing large URLs when you don't need to. Maybe you're storing a copy of browser headers a trillion times in your database. Add a bunch of those together and I could see a company storing massively more data per page. But I'm not convinced AirBnB needs it to track queries and clicks specifically. Or that they really need sub-click-resolution data.

by cdavid 4y ago

Dylan16807 4y ago

> Even using your numbers, if you want to keep say only 3 months of data, we're talking about 1-2 PB already. Am I doing the math wrong? "1 billion" was supposed to be lifetime stays, but let's say it's per year. Here's the math using 'my' numbers: 1 billion stays per year * 100 searches per stay * 150 bytes per search = 15TB per year 1 billion stays per year * 1000 page loads per stay * 15 bytes per page load = 15TB per year How are you getting petabytes? If 3 months is 1-2 hundred million stays, you'd need to store ten million bytes per stay to reach 1-2PB. (And images don't count, they wouldn't be in the database.)

cdavid 4y ago
> Am I doing the math wrong? Your mistake is to assume you need to look at per stay. You should look at per query if you want to improve your search. My math is based on the following: - 1000 qps - 1 query has on average 100 results - for each query you want to at least get the query string, the list of document ids, and the interaction for each document (view/click/etc.). So we're talking 1e3 (qps) * ~1e5 (seconds per day) * 1e2 = 10 billions events a day -> 1 peta events for 3 months. Even assuming 1 byte per event, and 1000 qps being super conservative for airbnb I suspect.
- Dylan16807 4y ago
  Your math is similar to mine, but you mixed up "tera" and "peta". 1000 billion events is 1 tera-event, and 0.001 peta-events.
  - cdavid 4y ago
    you're right about TB vs PB ofc :) But then keep in mind the assumptions were super conservative: * 1qps is likely off by at least half order magnitude * 1 byte per even is obviously off by several order of magnitudes, let's say just 1.5 order of magnitude. You need to know if an even is click/buy/view/..., you need the doc id that will likely be a 16 bytes uuid, etc. * etc. So you will reach the PB if not per a few month, but at least per year. sqlite or "simple" postgres really is not gonna cut it. I work in search for a C2C marketplace that is smaller than airbnb, and w/o going into details, we reach those orders of magnitude in big query.
    - Dylan16807 4y ago
      Okay, if you're going to try to inflate your estimate by 200x so you can get back to petabyte range then I'll do a more detailed comparison. > * 1qps is likely off by at least half order magnitude Wasn't your math based on a thousand queries per second? I don't think that's unreasonably small. And my math, in the "let's say it's 1 billion stays per year" version, assumes three thousand queries per second. And then you're assuming 100 clicks per query, a hundred thousand page loads per second. And I'm assuming 10 clicks per query, thirty thousand page loads per second. Are those numbers way too small? > * 1 byte per even is obviously off by several order of magnitudes, let's say just 1.5 order of magnitude. You need to know if an even is click/buy/view/..., you need the doc id that will likely be a 16 bytes uuid, etc. Sure, I think 30 bytes is reasonable for a click. When I said 15 I was squeezing a bit much. But timestamp, session ID, page template ID, property/comment/whatever ID, page number, click/buy/view byte if that isn't implied by page template... no need for that be more than 30 bytes total. 30 bytes per event * 30000 events per second * 1 year = only 2 hard drives worth of click data. And historically their stays were significantly less than they are today. > I work in search for a C2C marketplace that is smaller than airbnb, and w/o going into details, we reach those orders of magnitude in big query. Well there's a lot of factors here. Maybe your search results are a lot more complicated than "25-50 properties at a time". Maybe you're tracking more data than just clicks. Maybe you have very highly used pages that need hundreds of bytes of data to render. Maybe you're using UUIDs when much smaller IDs would work. Maybe you're storing large URLs when you don't need to. Maybe you're storing a copy of browser headers a trillion times in your database. Add a bunch of those together and I could see a company storing massively more data per page. But I'm not convinced AirBnB needs it to track queries and clicks specifically. Or that they really need sub-click-resolution data.