ACID principles

Atomicity

• Definition: A transaction is an all-or-nothing operation. Either every step in the transaction is completed successfully, or none of it happens.

example:

Bank Transfer: When transferring $100 from Account A to Account B, either:$100 is deducted from Account A and added to Account B, or no money is transferred at all. There cannot be a situation where money is deducted from one account but not added to the other.

Consistency

• Definition: A transaction must bring the database from one valid state to another, maintaining all rules and constraints.

example:
E-commerce Inventory: When an item is sold, the inventory count must decrease. If the count goes negative, the database is in an invalid state.

Isolation

• Definition: Transactions should not interfere with each other. The results of a transaction should not be visible to others until it is complete.

example:

Movie Ticket Booking: If two users are booking the last available seat, the database ensures only one transaction succeeds, preventing overselling.

Durability

• Definition: Once a transaction is committed, its changes are permanent, even if the system crashes.

example:

Online Order Placement: When an order is confirmed, it remains confirmed even if the server goes down right afterward.

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IOC

Inversion of Control (IOC) is a design principle in software development that means you reverse the way control is typically managed in a program. Instead of your code controlling the flow, it hands over that control to a framework or another system. This makes the program more flexible, modular, and easier to test.

Example:

Think of a restaurant’s kitchen:

• Without IOC: The manager constantly tells each chef what to cook and when.
• With IOC: The manager hands over control to a kitchen supervisor, who ensures everything is prepared as per orders.

Key Benefits of IOC

Decoupling: Components don’t need to know how other components work; they just rely on the framework to connect them.
Flexibility:Easier to swap out or update components without affecting others.
Testability: Components can be tested independently because they don’t directly depend on each other.

IOC in Frameworks

Spring Framework (Java):
Uses IOC to manage dependencies automatically through a container.
Example: You define beans (components) and let the framework inject dependencies.

Django (Python):
The framework decides how views, models, and templates are connected.

Angular (JavaScript):
Uses Dependency Injection (a form of IOC) to inject services into components.

Ref:https://medium.com/@kushanpeiris1118/most-common-interview-concept-what-are-solid-dry-and-acid-principles-937ca2945977