How do you ensure data consistency in MongoDB?

Data consistency in MongoDB can be ensured by using transactions. A transaction is a set of operations that are executed as a single unit and either all of them are applied or none of them are applied.

For example, if a customer wants to transfer money from one account to another, the transaction would include both the debit and credit operations. If either one of the operations fails, the entire transaction should be rolled back.

MongoDB provides the ability to use transactions across multiple documents, collections, and databases. This helps ensure data consistency by ensuring that all operations within the transaction are either all applied or none are applied.

What is sharding in MongoDB?

Sharding in MongoDB is a method for distributing data across multiple machines. It is a method for horizontal scaling, which allows a large dataset to be split across multiple servers or shards.

For example, let’s say you have a large dataset that is stored in a single MongoDB collection. To scale this dataset, you can use sharding to split the collection into multiple shards, each residing on a separate server. This would allow you to distribute the data across multiple machines, allowing for improved performance and scalability.

What is a replica set in MongoDB?

A replica set in MongoDB is a group of MongoDB instances that maintain the same data set. This means that each instance of the replica set contains the same data, and any changes made to the data on one instance will be automatically replicated to the other instances. For example, if you write a document to one instance, that document will be automatically replicated to the other instances in the replica set. Replica sets also provide redundancy and high availability, as they can continue to serve data even if one of the instances fails.

What is the difference between MongoDB and other traditional databases?

MongoDB is a NoSQL database, which differs from traditional relational databases such as MySQL, Oracle, and Microsoft SQL Server.

The main difference between MongoDB and traditional databases is that MongoDB stores data in documents instead of tables. Documents are collections of key-value pairs, similar to JSON objects. This allows MongoDB to store complex hierarchical data with ease. For example, a MongoDB document might look like this:

“name”: “John Smith”,
“age”: 35,
“address”: {
“street”: “123 Main St.”,
“city”: “New York”,
“state”: “NY”,
“zip”: 10001
“hobbies”: [“hiking”, “biking”, “swimming”]

Traditional databases typically require the data to be structured in a tabular format. This means that the data must be divided into rows and columns, which limits the types of data that can be stored. In contrast, MongoDB’s document-based structure allows for more flexibility in terms of data types, making it easier to store and query complex data.

What are the advantages of using MongoDB?

1. High Performance: MongoDB is designed to provide high performance data storage and retrieval. For example, when querying a large dataset, MongoDB can use an index to quickly locate the desired data.

2. Scalability: MongoDB is designed to scale easily and efficiently. It can be scaled up or down as needed, allowing applications to handle large volumes of data with ease.

3. Flexible Data Model: MongoDB uses a flexible data model, which makes it easier to store and query data. For example, MongoDB supports JSON documents, which can store data in a variety of formats, including objects, arrays, and strings.

4. High Availability: MongoDB is designed to provide high availability, meaning that applications can continue to operate even if there is a failure. For example, MongoDB can be configured to use replication, which allows multiple copies of the data to be maintained in different locations.

5. Rich Query Language: MongoDB provides a rich query language that allows developers to easily query and manipulate data. For example, MongoDB’s aggregation pipeline allows developers to perform complex data analysis tasks with ease.

What are the key features of MongoDB?

1. Document-oriented Storage: MongoDB stores data in JSON-like documents with dynamic schemas, making the integration of data in applications easier and faster. For example, a product document in MongoDB may look like this:
name: “Laptop”,
description: “Lenovo Thinkpad T480”,
price: 800

2. Indexing: MongoDB supports indexing on any field in a document which makes data retrieval faster. For example, if you want to find all the products with a price greater than $500, you can create an index on the price field and MongoDB will use it to quickly locate the documents you need.

3. Replication: MongoDB provides high availability with replica sets. A replica set consists of two or more copies of the data. All replica set members are synchronised, and one member is designated as the primary node, which receives all write operations. The other members, known as secondaries, replicate the primary’s data set.

4. Load balancing: MongoDB uses a technique called “sharding” to support deployments with very large data sets and high throughput operations. Sharding splits the data across multiple machines, so that the data can be spread out and accessed in parallel.

5. Aggregation: MongoDB has powerful aggregation capabilities that allow you to process large amounts of data and return computed results. For example, you can use the aggregation framework to calculate the average price of all the products in the collection.

What is the purpose of the initialize method in Ruby?

The initialize method is a special method in Ruby that is automatically called when an object is created. It can be used to set up or initialize any variables that the object will need when it is created.

For example, if you were creating a class to represent a Person, you might use the initialize method to set the person’s name and age:

class Person
def initialize(name, age)
@name = name
@age = age

person =“John”, 30)
puts person.inspect #

What is the purpose of the super keyword in Ruby?

The super keyword in Ruby is used to call a method from a parent or superclass. This is useful when you want to override a method in a subclass and still access the original method.

For example, say you have a superclass called Animal and a subclass called Cat. The Animal class has a method called speak that prints out “Meow”.

class Animal
def speak
puts “Meow”

class Cat Purr
# => Meow