# Plan

## Формализация задачи

функциональные требования (что пользователь хочет от системы в виде сценариев, jobs to be done)

нефункциональные требования (главные архитектурные характеристики: sizing, rps)

{% hint style="info" %}
определить важность и интересность требований, которую разбирать на собесе
{% endhint %}

## Границы системы

выбрать правильный способ интеграции системы: files, DB, API, messaging.

:white\_check\_mark: if (API) REST?, RPC?, GraphQL, AsyncAPI

:white\_check\_mark: выбрать сети и протоколы (TCP, UDP)

:white\_check\_mark: Балансировщики нагрузки (nginx, HAproxy)

обрабатываемые сценарии

```ini
NFR questions / aspects:
- DAU / MAU
- кол-во пользователей через 5-10 лет
- кол-во операций пользователем в день
- RPS, сетевой трафик, кол-во соединений
- CPU
- HDD / SSD (only 85% of disk space is available, 3-5% disks are destroyed over the year, do not forget about replication)
- $$$

~ 100_000 sec in a day (86400 accurately)
read 1MB sequentially from network ~ 10ms
read 1MB sequentially from disk ~ 30ms
Google SRE book with calcualtions (recommended to have a look)

TODO
- websocket vs long polling
```

## Потоки данных и компоненты системы

happy path. Read / write path

corner cases (когда части системы отваливаются). Уточнить на собесе что именно т до какой глубины здесь прорабатывать

проговорить логи, мониторинг, миграцию данных

TODO:

* stateless / stateful нагрузки (как разделять?)
* how to store documents in document oriented dbs
* :white\_check\_mark: repeat relations in DB ( 1 to many, etc)
* K/V, document oriented, column oriented, graph
  * по конкретным базам проработать
    * понять гарантии. Какой диапазон нагрузок они потянут. Дрифты часов
* :white\_check\_mark: :question:DDD
* :white\_check\_mark: Entity-Relationship diagram
* twelve factor app
* :white\_check\_mark: what is failure domains
* как масштабировать stateless/stateful компоненты на чтение, на запись (с использованием оркестраторов, горизонтальное, вертикальное)
  * :white\_check\_mark: partitioning vs sharding

Важно:

* задавать правильные вопросы
* не комититься на задачи, которые не нужно решать
* помнить о времени
* не начинать проектировать сразу
* делиться своими размышлениями на собесе
* проявлять самостоятельность и проактивность в проектировании
* реагировать на наводящие вопросы и уточнения
* в конце спросить и почему вы именно эту задачу спрашиваете? 

## :star:Systems to learn

for 10 euro here there are many of below systems designed [LINK](https://www.educative.io/courses/grokking-modern-system-design-interview-for-engineers-managers)

1. instagram
   1. [Feed, followers](https://www.youtube.com/watch?v=S2y9_XYOZsg)
   2. [Better about feed](https://www.youtube.com/watch?v=wYk0xPP_P_8)
2. :white\_check\_mark:tik tok
3. :white\_check\_mark:twitter (Twitter timeline and search) [LINK](https://github.com/donnemartin/system-design-primer?tab=readme-ov-file#system-design-interview-questions-with-solutions)
   1. [Timelines at Scale](https://www.infoq.com/presentations/Twitter-Timeline-Scalability/)
   2. [Operations at Twitter: Scaling Beyond 100 Million Users](https://www.youtube.com/watch?v=z8LU0Cj6BOU)
4. :white\_check\_mark:url shortener
5. :white\_check\_mark:uber [LINK](https://www.youtube.com/watch?v=Q7shD6ggYto)
6. :white\_check\_mark:доставка еды
7. :white\_check\_mark:whatsup
8. :white\_check\_mark:tinder [Example](https://www.youtube.com/watch?v=tndzLznxq40\&t=1691s)
9. netflix
   1. [Scaling Push Messaging for Millions of Devices](https://www.youtube.com/watch?v=6w6E_B55p0E)
10. Pastebin.com [LINK](https://github.com/donnemartin/system-design-primer?tab=readme-ov-file#system-design-interview-questions-with-solutions)
11. web crawler [LINK](https://github.com/donnemartin/system-design-primer?tab=readme-ov-file#system-design-interview-questions-with-solutions)
12. Mint.com [LINK](https://github.com/donnemartin/system-design-primer?tab=readme-ov-file#system-design-interview-questions-with-solutions)
13. facebook
    1. [Scaling Memcache at Facebook](https://www.usenix.org/conference/nsdi13/technical-sessions/presentation/nishtala)
    2. [Scaling Facebook Live Videos to a Billion Users](https://www.youtube.com/watch?v=IO4teCbHvZw)
    3. [Feed, followers](https://www.youtube.com/watch?v=S2y9_XYOZsg)
    4. [Better about feed](https://www.youtube.com/watch?v=wYk0xPP_P_8)
14. data structures for a social network [LINK](https://github.com/donnemartin/system-design-primer?tab=readme-ov-file#system-design-interview-questions-with-solutions) 
    1. In details [Facebook’s Distributed Data Store for the Social Graph](https://www.usenix.org/conference/atc13/technical-sessions/presentation/bronson)
15. key-value store for a search engine [LINK](https://github.com/donnemartin/system-design-primer?tab=readme-ov-file#system-design-interview-questions-with-solutions)
16. Amazon's sales ranking by category feature [LINK](https://github.com/donnemartin/system-design-primer?tab=readme-ov-file#system-design-interview-questions-with-solutions)
17. [Introducing Non-Abstract Large System Design](https://sre.google/workbook/non-abstract-design/)
18. :white\_check\_mark:[Capacity planning and hardware selection for DataStax Enterprise implementations](https://docs.datastax.com/en/dseplanning/docs/dse-capacity-planning.html)
19. [Пройти беларуса](https://www.youtube.com/channel/UC9vLsnF6QPYuH51njmIooCQ)
20. [YouTube Scalability](https://www.youtube.com/watch?v=ZW5_eEKEC28)
21. :white\_check\_mark:[Using logs to build a solid data infrastructure](https://www.confluent.io/blog/using-logs-to-build-a-solid-data-infrastructure-or-why-dual-writes-are-a-bad-idea/)
22. :white\_check\_mark:Dropbox [LINK](https://www.youtube.com/watch?v=lamooN_E5aY)

[Back of the envelope calculations](https://www.teamblind.com/post/rBrt5bV8) (good example [LINK](https://ishan-aggarwal.medium.com/back-of-the-envelope-estimation-8e0cdba19a68))

[A lot of links are taken from here](https://www.teamblind.com/post/qubF6fS2)

Great youtube channel [Crushing Tech Education](https://www.youtube.com/@crushingtecheducation/videos); [Jordan has no life](https://www.youtube.com/@jordanhasnolife5163/videos)


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