System Design 1

Question 1

It means increasing the resources of a specific node

Answer 1

Vertical Scaling

Question 2

It means increasing the number of nodes

Answer 2

Horizontal Scaling

Question 3

It allows a system to distribute the load evenly so that one server doesn’t crash and take down the whole system.

Answer 3

Load Balancer

Question 4

They can get very slow as the system grows bigger.

Answer 4

Joins in a relational database such as SQL.

Question 5

It means splitting the data across multiple machines while ensuring you have a way of figuring out which data is on which machine.

Answer 5

Sharding (Data partitioning)

Question 6

Common ways of partitioning:

Answer 6

• Vertical Partitioning
• Key-Based (or Hash-Based) Partitioning
• Directory-Based Partitioning

Question 7

Partitioning by feature.

e.g. In a social network you have a table for profiles, one for messages

Answer 7

Vertical Partitioning

Question 8

It uses some kind of data (e.g. an ID) for the partition.

Answer 8

Key-based Partitioning.

Question 9

A very simple way to do this is to allocate N servers and put the data on mod(key, n)

Answer 9

Key-based Partitioning

Question 10

In this scheme you maintain a lookup table for where the data can be found

Answer 10

Directory-Based Partitioning

Question 11

Two major drop backs in Directory-Based Partitioning:

Answer 11

1. The lookup table can be a single point of failure.
2. Constantly accessing this table impacts performance.

Question 12

It is a simple key-value pairing and typically sits between your application layer and the data store.

Answer 12

Caching.

Question 13

How you cache

Answer 13

You might cache a query and its results directly. Or alternatively you can cache the specific object (a rendered version of the website or a list of the most recent blog posts)

Question 14

Most important metrics around networking

Answer 14

Bandwidth, throughput, latency

Question 15

How slow operations should be

Answer 15

Asynchronous

Question 16

Is the maximum amount of data that can be transferred in a unit of time, it is expressed in bits per second.

Answer 16

Bandwidth

Question 17

Is the actual amount of data that is transferred.

Answer 17

Throughput

Question 18

It is how long it takes data to go from one end to the other.

Answer 18

Latency

Question 19

It is typically used to process large amounts of data.

Answer 19

A MapReduce program.

Question 20

What does a MapReduce program require.

Answer 20

It requires to write a Map step and Reduce step.

Map takes in some data and emits a <key, value> pair.
Reduce takes a key and a set of associated values and “reduces” them, emitting a new key and value.

Question 21

Considerations when designing a system.

Answer 21

• Failures
• Availability and Reliability
• Read-Heavy vs Write-Heavy
• Security

Question 22

Is a function of the percentage of time the system is operating.

Answer 22

Availability.

Question 23

Is a function of the probability that the system is operational for a certain unit of time.

Answer 23

Reliability.

Question 24

You could consider queuing up the writes-

Answer 24

Write-Heavy.

Question 25

Yo might want to cache.

Answer 25

Read-Heavy

Question 26

It's a network of servers located all around the world.

Answer 26

CDN (Content Delivery Network)

Question 27

CDN specifications

Answer 27

1.They don't really run any application logic. 2. They work by taking files hosted on your server (origin server) and copy them onto CDN servers. 3. It's a technique of caching.

Question 28

It's the set of rules that decide how we send data over the internet. Works with packets.

Answer 28

TCP/IP

Question 29

It's a decentralized service that works to translate a domain (eg. www.leetcode.com) to it's IP address (192.0.2.132)

Answer 29

DNS (Domain Name System)

Question 30

Is an application level protocol built on top of TCP that follows the client-server model.

Answer 30

HTTP

Question 31

How does HTTP work?

Answer 31

A client initiate a request, which include two parts: request header and request body. Then the client will receive a response.

Question 32

Information in the Request Header

Answer 32

Where the package is going, who it's from and other metadata.

Question 33

Request Body:

Answer 33

It's the package content.

Question 34

Is a standardization around HTTP APIs making them stateless and following consistent guidelines.

Answer 34

REST

Question 35

What is GraphQL?

Answer 35

API pattern. Instead of making another request for every single resource in your server, you make a single request and choose which resources to fetch, you can fetch multiple resources with a single request.

Question 36

What is gRPC?

Answer 36

Framework, considered an improvement of JSON. Is mainly used for server-to-server communication. Data is serialized into a binary format, although, JSON is more human readable.

Question 37

App layer protocol that supports bidirectional communication:

Answer 37

WebSockets

Question 38

Relational Databases. Provides efficient storage and fast power retrieval.

Answer 38

SQL

Question 39

ACID.

Answer 39

* Atomicity * Consistency * Isolation * Durability

Question 40

Every transaction is fully performed or not performed at all.

Answer 40

Atomicity.

Question 41

Means that foreign keys and other constraints are enforced.

Answer 41

Consistency (Database).

Question 42

Means that different concurrent transactions won't interfere with each other.

Answer 42

Isolation.

Question 43

Even if a machine dies data will still be there.

Answer 43

Durability.

Question 44

No-SQL databases examples.

Answer 44

Key-value stores, document stores and Graph DBs.

Question 45

Refers to the process of creating and maintaining multiple copies of data or system components.

Answer 45

Replication

Question 46

This states that it is not possible for a distributed computer system to simultaneously provide all three of guarantees.

Answer 46

CAP (Consistency, Availability and Partition) Theorem.

Question 47

All nodes see the same data even at the same time with concurrent updates

Answer 47

Consistency.

Question 48

A guarantee that every request receives a response about whether it was successful or failed.

Answer 48

Availability

Question 49

The system continues to operate despite arbitrary message loss or failure of part of the system.

Answer 49

Partition Tolerance.

Question 50

Is an XML based industry standard protocol for designing and developing web services.

Answer 50

SOAP (Simple Object Access Protocol)

Question 51

Is a software design approach that organizes applications as a collection of services.

Answer 51

SOA (Service Oriented Architecture)

Question 52

How does SOA work?

Answer 52

The services communicate with each other through well-defined interfaces, often using standard protocols like SOAP or REST.

Question 53

Key Characteristics of SOA.

Answer 53

* Loose Coupling * Reusability * Modularity * Interoperability

Question 54

Desine Loose Coupling

Answer 54

Services are independent and can be modified without affecting other services.