System Design

Question 1

What is impractical about having one server and a database for designing a system?

Answer 1

It’s not scale able, as the user base grows

Question 2

What is the solution to having one server and a database?

Answer 2

Distributed system

Question 3

What is a distributed System?

Answer 3

A network of standalone computers that work together as one

Question 4

What are the key characteristics of a distributed system?

Answer 4

• Scalability
• Reliability
• Availability
• Efficiency

Question 5

What is scalability in terms of system designg?

Answer 5

The systems ability to handle growing demand

Question 6

What is horizontal scaling in system design?

Answer 6

Scale by increasing the amount of servers

Question 7

What is vertical scaling?

Answer 7

Scale by adding more/upgrading resources

Question 8

What is a reliable system?

Answer 8

The system remains to operate even when components fail

Question 9

What is availability in terms of system design?

Answer 9

The percentage of time a system is available

Question 10

What is efficiency in terms of system design?

Answer 10

Latency - The delay in getting the first response
Throughput - Operations per time unit

Question 11

What is the typical trade-off when designing distributed systems?

Answer 11

Scalability vs consistency

Question 12

What is a load balancer?

Answer 12

Balances the load of traffic to each working server on a system

Question 13

What are some of the load balancer algorithms?

Answer 13

Least connection - Sends requests to the server with the least connections
Round Robin - Iterates through a list of servers
IP Hash - Uses clients IP to identify which server

Question 14

Can load balancers fail?

Answer 14

Yes, they can become a single point of failure, therefore it is advised to have standby load balancers in case one fails.

Question 15

What is caching in system design?

Answer 15

Stores recent retrieved data as it anticipates it will be needed again

Question 16

What are some issues that arise with caching?

Answer 16

Data consistency, we must ensure that the cache data is accurate

Question 17

How does SQL/relational databases store data?

Answer 17

Stores data in tables with predefined schema

Question 18

What are NoSQL Databases?

Answer 18

More flexible data-structure than SQL

Question 19

What are the four main types of NoSQL databases?

Answer 19

• Key-Value Stores
• Document Database
• Wide-column Stores
• Graph Databases

Question 20

What do we compare when SQL vs NoSQL?

Answer 20

• Structure: SQL has a rigid schema, NoSQL is more flexible
• Querying: SQL uses more structured querying, NoSQL is more focused on collection of documents
• Scalability: SQL vertical scaling, NoSQL horizontal scaling
• Reliability: SQL is ACID compliant, NoSQL is not

Question 21

When would we use SQL (systems)?

Answer 21

• ACID Compliance is needed
• Financial Applications
• Structured Consistent data

Question 22

When would we use NoSQL (systems)?

Answer 22

• Large volumes of unstructured data
• Flexibility in data structures
• In need of rapid development that requires change

Question 23

How do we upgrade database quering speed?

Answer 23

• Indexing - a structure that points to the actual location of the data

Question 24

What is indexing tradeoffs?

Answer 24

Improve read performance at the cost of write performance

Question 25

What can you do when a database can no longer scale vertically?

Answer 25

Data partitioning

Question 26

What is data partitioning?

Answer 26

Breaking a database into smaller manageable partitions

Question 27

What are different database partitioning methods?

Answer 27

- Horizontal Partitioning (Sharding) - Vertical Partitioning - Directory-based Partitioning

Question 28

What is horizontal partitioning (sharding)?

Answer 28

Divides rows of a table into separate databases

Question 29

What is vertical partitioning?

Answer 29

Separating features or columns into separate databases

Question 30

What is directory-based partitioning?

Answer 30

Uses a look-up service to abstract a partitioning scheme

Question 31

What are some partitioning techniques?

Answer 31

- Using hash functions - List partitioning - Round robin

Question 32

What is the hash function partitioning technique?

Answer 32

Applying a hash function to the key to determine which partition to put the data in

Question 33

What is the list partitioning technique?

Answer 33

Assign each partition a list of values and storing data based on which list it's assigned to

Question 34

What is the round robin partition?

Answer 34

Distribute data evenly through partitions in a circular order

Question 35

What is composite partitioning?

Answer 35

Partition that combines two or more partition methods

Question 36

What are the benefits and drawbacks of partitioning?

Answer 36

Solves scaling issues, but introduces the challenge of joining of data across multiple partitions