REST API -two or more software components interact with each other

 

API stands for Application Programming Interface. It is a set of rules and specifications that define how two or more software components interact with each other. 

APIs are used to allow different applications to communicate with each other and share data.

APIs are used in a wide variety of applications, including:

• Web services: APIs are used to power web services, such as Google Maps API, Twitter API, and Facebook Graph API. These APIs allow developers to build applications that can interact with the underlying web services.
• Mobile apps: APIs are used to power many mobile apps. For example, a weather app might use an API to retrieve weather data from a weather service.
• IoT devices: APIs are used to connect and control IoT devices. For example, a smart home system might use an API to control a smart thermostat.

APIs can be either public or private. Public APIs are available to anyone who wants to use them. Private APIs are only available to authorized users.

To use an API, you typically need to get an API key from the API provider. This key identifies you as an authorized user of the API. Once you have an API key, you can start making requests to the API.

API requests are typically made using HTTP. The request body contains the information that you need to send to the API. The response body contains the information that the API returns to you.

APIs are a powerful tool for building and integrating software applications. By understanding how APIs work, you can build more efficient, effective, and scalable applications.

Here are some examples of how APIs are used in the real world:

• When you use a ride-sharing app to book a ride, the app uses an API to communicate with the ride-sharing company's servers. The app sends the pickup and drop-off locations to the servers, and the servers send back the estimated fare and arrival time.
• When you use a social media app to post a photo, the app uses an API to communicate with the social media company's servers. The app sends the photo and any accompanying text to the servers, and the servers post the photo to your profile.
• When you use a shopping app to purchase an item, the app uses an API to communicate with the retailer's servers. The app sends your shipping and billing information to the servers, and the servers process the payment and ship the item to you.

REST 

REST stands for REpresentational State Transfer. It is an architectural style for designing and developing web services. REST is based on the idea of using resources and their representations to provide a uniform interface for accessing and manipulating data.

RESTful web services are characterized by the following principles:

• Client-server separation: The client and server are separate components that communicate with each other using a stateless protocol.
• Statelessness: Each request from the client contains all of the information necessary to understand and process the request. The server does not maintain any state about the client between requests.
• Cacheability: The client can cache responses from the server to improve performance.
• Layered system: The system is composed of multiple layers, each of which has a specific responsibility. This makes the system more modular and easier to maintain.
• Code on demand (optional): The server can send executable code to the client to be executed on the client side. This can improve performance and flexibility.

REST is a popular architectural style for web services because it is simple, flexible, and scalable. It is also well-suited for distributed systems and cloud computing.

Here are some examples of RESTful web services:

• Google Maps API
• Twitter API
• Facebook Graph API
• Amazon Web Services API
• GitHub API

REST is a powerful architectural style for designing and developing web services

API is a broader term that refers to any interface that allows two or more software components to interact with each other. REST is a specific architectural style for designing and developing APIs.

RESTful APIs are characterized by their use of HTTP verbs to represent different operations, such as GET for retrieving data and POST for creating new data. They also use URIs to identify resources and JSON or XML to represent data.

Here is a table that summarizes the key differences between REST and API:

Feature	REST	API
Architectural style	Yes	No
HTTP verbs	Yes	No
URIs	Yes	No
Data representation	JSON or XML	Any format
Statelessness	Yes	No (optional)
Cacheability	Yes	No (optional)
Layered system	Yes	No (optional)
Code on demand	Yes	No

RESTful APIs are the most common type of API, and they are used by many popular web services, such as Google Maps API, Twitter API, and Facebook Graph API.

Here are some examples of RESTful APIs:

• Google Maps API: This API allows developers to retrieve and display maps, directions, and traffic information.
• Twitter API: This API allows developers to retrieve and post tweets, follow and unfollow users, and search for tweets.
• Facebook Graph API: This API allows developers to retrieve and post user data, publish and manage content, and manage ads.

RESTful APIs are a popular choice for developers because they are simple, flexible, and scalable. They are also well-suited for distributed systems and cloud computing.

Oracle Cloud Infrastructure Q n A

 Different types of compute instances available in OCI:

• General purpose
• Compute optimized
• Memory optimized
• Accelerated computing
• Bare metal

Different types of storage available in OCI:

• Block storage
• Object storage
• File storage
• Archive storage

Different types of networking resources available in OCI:

• Virtual cloud networks (VCNs)
• Subnets
• Security lists
• Route tables
• Gateways
• Load balancers

Different types of databases available in OCI:

• Autonomous Database
• Database Service for Oracle Database
• Database Service for MySQL
• Database Service for PostgreSQL
• Database Service for NoSQL

Different types of analytics and AI services available in OCI:

• Analytics Cloud
• AI Platform
• Data Science Workbench
• Data Catalog
• Databricks in OCI

Different types of app development services available in OCI:

• Container Engine for Kubernetes (OKE)
• Cloud Native Applications Platform (CNAP)
• Functions
• API Gateway
• Service Mesh
• Mobile Backend as a Service (MBaaS)

Different types of security and compliance services available in OCI:

• Identity and Access Management (IAM)
• Key Management
• Security Zones
• Security Audit and Monitoring
• Data Governance
• Compliance

Different types of identity and access management services available in OCI:

• Identity and Access Management (IAM)
• Identity Cloud Service (IDCS)
• Unified Directory
• Access Management
• Identity Analyzer

Different types of observability and management services available in OCI:

• Monitoring
• Logging
• Analytics
• Notifications
• Cost Management
• Resource Manager

Different types of hybrid offerings available in OCI:

• Dedicated Region Cloud@Customer
• Managed Cloud@Customer
• Oracle Cloud VMware Engine
• Oracle Cloud Exadata Cloud Service
• Oracle Cloud Infrastructure FastConnect

A boot volume is a type of block volume that is used to boot a compute instance. It contains the operating system and all of the files required to start the instance. A block volume is a general-purpose storage device that can be used to store any type of data.

Boot volumes are typically smaller than block volumes, as they only need to contain the operating system and boot files. They are also typically configured to be more performant than block volumes, as they need to be able to quickly read and write data during the boot process.

Block volumes can be of any size and can be used to store any type of data, including operating systems, databases, applications, and user files. They are typically less expensive than boot volumes, but they may not be as performant.

Use cases for boot volumes:

• Booting a compute instance with an operating system
• Creating a bootable image for a compute instance
• Recovering a compute instance from a backup

Use cases for block volumes:

• Storing an operating system for a compute instance
• Storing data for a database or application
• Storing user files
• Creating a snapshot of a volume for backup or recovery

Example:

You can use a boot volume to install an operating system on a compute instance. Once the operating system is installed, you can use the boot volume to boot the instance. You can also use a boot volume to create a bootable image for a compute instance. This can be useful for quickly deploying multiple instances with the same operating system and configuration.

You can use a block volume to store data for a database or application. You can also use a block volume to store user files. Block volumes can be attached to multiple compute instances, so you can share data between instances. You can also create a snapshot of a block volume for backup or recovery.

A public IP address is a unique IP address that is assigned to your network router by your internet service provider (ISP). It is used to identify your router and your devices on the internet.

A private IP address is a unique address that is assigned to a device on a local network. It is used to identify the device within that network.

Use cases for public IP addresses:

• Hosting a website or web server
• Playing online games
• Using remote desktop software to access a computer on your home network from outside of your home

Use cases for private IP addresses:

• Connecting to a printer on a local network
• Sharing files between devices on a local network
• Playing multiplayer games on a local network

Example:

When you visit a website, your computer sends a request to the website's server. The server then sends back the website's content to your computer. In order for the server to know where to send the website's content, it needs to know your computer's IP address.

If your computer has a public IP address, the server can send the website's content directly to your computer. However, if your computer has a private IP address, the server will not be able to send the website's content directly to your computer. Instead, the server will send the website's content to your router. Your router will then forward the website's content to your computer.

This process is called network address translation (NAT). NAT is used to allow multiple devices on a local network to share a single public IP address.

differences between NAT gateways and load balancers:

NAT gateway is a managed network service that allows instances in a private subnet to access the internet. It does this by translating the private IP addresses of the instances to a single public IP address. This allows the instances to send and receive traffic from the internet, even though they do not have their own public IP addresses.

A load balancer is a device or software that distributes traffic across multiple servers. This can help to improve performance, reliability, and scalability. Load balancers can be used to distribute traffic between web servers, application servers, and database servers.

Use cases for NAT gateways:

• Allowing instances in a private subnet to access the internet
• Providing internet access to devices on a local network

Use cases for load balancers:

• Distributing traffic across multiple web servers
• Distributing traffic across multiple application servers
• Distributing traffic across multiple database servers
• Improving performance, reliability, and scalability of applications

Example:

A company has a website that is hosted on two web servers in a private subnet. The company wants to allow users to access the website from the internet. The company can use a NAT gateway to translate the private IP addresses of the web servers to a single public IP address. This will allow users to access the website by visiting the public IP address in a web browser.

The company could also use a load balancer to distribute traffic between the two web servers. This would help to improve performance and reliability. If one web server goes down, the load balancer will continue to distribute traffic to the other web server.

Conclusion:

NAT gateways and load balancers are both network devices that can be used to improve the performance, reliability, and scalability of applications. However, they have different purposes. NAT gateways are used to allow instances in a private subnet to access the internet, while load balancers are used to distribute traffic across multiple servers

database instance and a database cluster

eature	Database Instance	Database Cluster
Definition	A single running instance of a DBMS	A group of database instances that work together as a single system
Purpose	To store, manage, and access data	To improve performance, scalability, and high availability
Scalability	Limited to the resources of a single server	Can be scaled up or down by adding or removing database instances
Availability	Can be unavailable if the server fails	Can remain available even if one or more database instances fail

 some examples of database clusters:

• A cluster of web servers that use a database to store user data
• A cluster of database servers that support a large online transaction processing (OLTP) system
• A cluster of database servers that store and analyze big data

differences between VCNs and subnets:

VCNs and subnets are essential components for creating secure and scalable networks in OCI.

A virtual cloud network (VCN) is a software-defined network that you create and manage in Oracle Cloud Infrastructure (OCI). A VCN is isolated from other VCNs and the public internet, which provides security and control over your network traffic.

A subnet is a subdivision of a VCN. Subnets are used to organize your resources within a VCN and to control network traffic between them. You can create multiple subnets in a VCN, each with its own range of IP addresses.

differences between VCNs and subnets:

Feature	VCN	Subnet
Definition	A software-defined network that you create and manage in OCI	A subdivision of a VCN
Purpose	To isolate your resources from other VCNs and the public internet	To organize your resources within a VCN and to control network traffic between them
Size	A VCN can have up to 100 subnets	A subnet can have up to 4 billion IP addresses
Scope	A VCN is global to a region	A subnet is regional

security list and a network access control list (NACL)?

A security list and a network access control list (NACL) are both firewall-like features that can be used to control traffic in and out of a network. However, there are some key differences between the two.

Scope

• A security list is associated with an instance, while a NACL is associated with a subnet. This means that a security list controls traffic to and from a specific instance, while a NACL controls traffic to and from all instances in a subnet.

Rules

• Security list rules can be used to allow or deny traffic based on the source IP address, destination IP address, port number, and protocol. NACL rules can also be used to allow or deny traffic based on the same criteria, but they can also be used to block specific IP addresses or ports.

Statefulness

• Security lists are stateful, meaning that they keep track of the state of connections and allow traffic in both directions for established connections. NACLs are stateless, meaning that they only evaluate traffic based on the individual packets, not the state of the connection.

Use cases

• Security lists are typically used to control traffic to and from specific instances, such as web servers or database servers. NACLs are typically used to control traffic to and from all instances in a subnet, such as a subnet that contains public-facing web servers.

What is the difference between a database role and a database user?

A database role is a logical grouping of permissions that can be assigned to database users. A database user is an individual user account that can be used to access a database.

Roles can be used to simplify permission management by assigning a single role to a group of users with similar needs. For example, you could create a role for developers that gives them permission to create and modify database objects, and a role for administrators that gives them permission to manage all aspects of the database.

Users can be assigned to multiple roles, and the permissions of all roles assigned to a user are combined. For example, a user who is assigned to both the developers role and the administrators role would have all of the permissions granted to both roles.

What is the difference between a database snapshot and a database backup?

A database snapshot is a point-in-time copy of a database. A database backup is a copy of the database that is typically used to recover from data loss or corruption.

Snapshots can be used to create test environments, to back up databases before making changes, or to restore databases to a previous point in time. Snapshots can be created quickly and easily, and they can be used to restore databases to their previous state just as quickly.

Backups are typically created on a regular schedule, such as daily or weekly. They can be stored on-premises or in the cloud. Backups are used to recover from data loss or corruption, such as if a database is accidentally deleted or corrupted.

What is the difference between a database instance resize and a database instance move?

A database instance resize is the process of changing the size of a database instance. This can be done to increase or decrease the resources allocated to the instance.

A database instance move is the process of moving a database instance to a different physical or virtual machine. This can be done for a variety of reasons, such as to improve performance or to migrate the instance to a different region.

What is the difference between a load balancer and a web application firewall (WAF)?

A load balancer distributes traffic across multiple servers. This can be used to improve performance and scalability, and to ensure that applications remain available even if one server fails.

A web application firewall (WAF) protects web applications from attacks. WAFs can be used to block common web attacks, such as SQL injection and cross-site scripting.

Load balancers and WAFs can be used together to improve the performance, scalability, and security of web applications.

Windows services that can slow down your computer,

 

• SuperFetch:(Sysmain) This service pre-loads frequently used programs into memory, which can improve startup times and application performance. However, it can also use up a lot of memory, especially on older computers.
• Windows Search: This service indexes your files and folders so that you can quickly find them. However, it can also use up a lot of CPU resources, especially when it's first running.
• Print Spooler: This service manages your printing jobs. However, it can sometimes get stuck or cause problems, which can slow down your computer.
• OneDrive: This service syncs your files and folders between your computer and the cloud. However, it can use up a lot of CPU and network resources, especially when it's first syncing or uploading large files.
• Other services that you don't need: There are a number of other Windows services that you may not need, such as those for games, peripheral devices, or programs that you no longer use. Disabling these services can free up resources and improve your computer's performance.

There are a number of Windows services that can slow down your computer, especially if you don't need them. Some of the most common include:

• Superfetch: This service pre-loads frequently used programs into memory, which can improve startup times and application performance. However, it can also use up a lot of memory, especially on older computers.
• Windows Search: This service indexes your files and folders so that you can quickly find them. However, it can also use up a lot of CPU resources, especially when it's first running.
• Print Spooler: This service manages your printing jobs. However, it can sometimes get stuck or cause problems, which can slow down your computer.
• OneDrive: This service syncs your files and folders between your computer and the cloud. However, it can use up a lot of CPU and network resources, especially when it's first syncing or uploading large files.
• Other services that you don't need: There are a number of other Windows services that you may not need, such as those for games, peripheral devices, or programs that you no longer use. Disabling these services can free up resources and improve your computer's performance.

It's important to note that you should be careful about disabling Windows services. Some services are essential for the proper operation of your computer and disabling them can cause problems. If you're not sure whether or not you need a particular service, it's best to leave it enabled.

If you're experiencing performance problems, you can try disabling some of the services listed above to see if that helps. You can do this by opening the Services console (press Windows key + R and type "services.msc"). Once the Services console is open, scroll down to the service you want to disable and double-click it. In the Startup type drop-down menu, select Disabled. Click OK to save your changes.

It's also important to note that disabling services is not a permanent solution. If you need to use a service again, you can simply re-enable it following the steps above.

Here are some additional tips for speeding up your windows computer:

• Uninstall any programs that you don't use.
• Clean up your hard drive by deleting temporary files and other junk.
• Defragment your hard drive.
• Update your drivers.
• Add more RAM.
• Use a SSD instead of a traditional hard drive.

Reference: Google