System Design

Question 1

Define: relational database. Give an example.

Answer 1

• Database built around tables.
• They often have keys that point to other values in other tables.
• MySQL is an example
• example implementation: set of tables for a blog: posts, comments, hashtags each have their own table, all linked via some key like ID

Question 2

Define: non-relational database Give an example.

Answer 2

• does not use a table
• all data linked in one hierarchy
• NoSQL is an example, Firebase Store is an example
• example implementation: blog object, that has posts, comments, and hashtags within it

Question 3

What type of database uses tables, rows, and keys?

Answer 3

Relational db

Question 4

Give an example of a relational db

Answer 4

MySQL

Question 5

Give an example of a non-relational db

Answer 5

NoSQL

Question 6

You’re given a prompt to design some app, what questions do you ask understand the problem statement?

Answer 6

• what are we being asked to design?
• who is the user and how will they use this system?
• which parts of the system are we expected to design? ie only the core UX? mobile vs web?

Question 7

Give an example of how you would narrow down the scope of a prompt to system design an app such as netflix

Answer 7

We could look at the purchasing UX, or the core viewer UX, or the media producer UX. Let’s start with core viewer UX. What features within the coreUX do we wanna focus on? So maybe we can start from the content-detail screen, as well was the viewing experience, the post-viewing exerperience UX

Question 8

is this an example of relational or non relational db? why?

https://imgur.com/XjVAe2V

Answer 8

relational bc there are tables and they are linked by some key

Question 9

is this an example of relational or non relational db? why?

https://imgur.com/tKpEeyu

Answer 9

Non relational bc there are no tables and bc there is a hierarchy of data

Question 10

Define concurrency

Answer 10

Executing multiple tasks at the same time but not necessarily simultaneously

Question 11

What are message queues used for?

Answer 11

• makes it possible for applications to communicate and perform work asynchronously
• example, if posting a tweet, the tweet could be instantly posted to your timeline, but it could take some time before your tweet is actually delivered to all of your followers.

Question 12

Give an example of what a message queue could be used for

Answer 12

For example, if posting a tweet, the tweet could be instantly posted to your timeline, but it could take some time before your tweet is actually delivered to all of your followers.

Question 13

Give an example of a message queue tool

Answer 13

Redis (can also do other things)

Question 14

Define: queue. Give an example.

Answer 14

A line of things waiting to be handled, such as a messaging queue that holds a list of messages to deliver asynchronously.

Question 15

What are some problems with concurrency?

Answer 15

• race conditions

- deadlocks

Question 16

When should you use a relational db?

Answer 16

When you need to store predictable, structured data with a relational use-case, such as a social network

Question 17

When should you use a non-relational database?

Answer 17

When you have flexible, dynamic, changing data storage requirements.