Database Replication | Synchronous vs Asynchronous | System Design Interview Question | Code Decode

In this video of System design code decode have explained data base replication.
This is very important system design interview question.

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Scenarios where we need to choose between NOSQL DB and relational DBs ?

Scenario 1: READ Vs WRITE Intensive Application

When your application is read intensive the use NOSQL db .

If the application is Write Intensive then go for Relational DB.

Why ? If we have to read a lot and update less, then having multiple relational DBs and having join queries to read a lot of data base will decrease the performance. So better go with Non relational DBs. Now everything will be in one document and no joins, views complex queries wool be required which decreases the readability, performance , speed and other non functional parameters of aplication


Scenario 2: Unstructured VS Structured Data

When your application is going to persist the data which is not structured, there is no guarantee on how many fields we will get and we need to store then its unstructured data. Then go for No sql DB choice as there is no restriction on columns or fields in which data has to be inserted .

But If we are very sure the data structure wont change ever in whole life cycle of application then even relational DB is also a good choice

Scenario 3: Concurrency and atomicity is top priority

In applications like hotel / movie ticket booking - Several users simultaneously read and write the data.

To prevent data inconsistency, such as the double booking of hotel rooms, we must coordinate such transactions.

Transactional access to the data in a relational database manages concurrency.

A transaction is regarded as an atomic operation, making it possible to roll back or commit a transaction after a successful execution in error handling.


To facilitate this feature we need Relational Dbs .

Scenario 4: Cost associated

If we are allotted a very less budget for the project, go for open source NO Sql db as many NoSQL databases are open source and freely available..

While with Relational DBs, these are not open source usually n we need to purchase the License for it.



Scenario 5: Redundancy tolerance

Eliminating data redundancy is one of the relational database's main benefits.

One table contains information about a particular entity, whereas other tables connected by foreign keys include information pertinent to that entity.


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