How do NoSQL databases work? Simply Explained!

Summary

NoSQL databases are gaining popularity for their scalability and flexibility, especially in handling large volumes of data. Unlike traditional relational databases which struggle with scaling due to their complex relational structures, NoSQL databases, such as DynamoDB, BigTable, and CosmosDB, offer both vertical and horizontal scaling. They function as key-value stores, simplifying data management and enabling efficient distribution across multiple servers. Despite their advantages, NoSQL databases have limitations in data retrieval and consistency, making them a complementary choice to relational databases for specific use cases.

Takeaways

• 📈 NoSQL databases are popular for their ability to handle large volumes of data and high query loads, as seen in big companies.
• 🔄 Traditional relational databases like MySQL and SQL Server are efficient for relational data but struggle with scaling due to the need to maintain data relationships.
• 🔄 NoSQL databases excel in scalability, offering both vertical and horizontal scaling, compared to the vertical-only scaling of relational databases.
• 🏢 The concept of scaling can be visualized as adding floors to a building for vertical scaling and constructing new buildings for horizontal scaling.
• 🔑 NoSQL databases function as key-value stores, simplifying data storage without the overhead of maintaining relationships between data items.
• 📦 Items in NoSQL databases are stored based on partitions determined by a hash function applied to the primary key, allowing for efficient distribution across servers.
• 📈 Apple's use of a NoSQL database with 75,000 servers exemplifies the massive scalability of these databases.
• 🗂 NoSQL databases are schemaless, allowing for flexible and evolving data structures without the constraints of a predefined schema.
• 🔍 NoSQL databases have limitations in data retrieval, primarily allowing access via primary keys, which can be inefficient for certain queries.
• 🔄 The eventual consistency model of NoSQL databases means that data may not immediately reflect writes due to replication delays across servers.
• 🌐 Major cloud providers offer NoSQL databases like AWS DynamoDB, Google BigTable, and Azure CosmosDB, highlighting their importance in cloud infrastructure.
• 🤔 The term 'NoSQL' can be interpreted as 'not only SQL', indicating some support for SQL queries, or 'non-relational', emphasizing the difference from traditional relational databases.

Q & A

What is the primary reason NoSQL databases have become popular?

NoSQL databases have become popular due to their ability to handle large volumes of data and run a high number of queries per second, which traditional relational databases struggle with.

Why do relational databases have difficulty scaling?

Relational databases have difficulty scaling because they need to maintain relationships between data, which is an intensive process requiring a lot of memory and compute power.

What is the difference between vertical and horizontal scaling in the context of databases?

Vertical scaling refers to adding more resources to an existing server, like adding floors to a building. Horizontal scaling refers to adding more servers to distribute the workload, similar to adding more buildings.

How do NoSQL databases eliminate the need for maintaining relationships between data?

NoSQL databases work as key-value stores, where each item stands on its own without the need for maintaining relationships, simplifying the data structure and allowing for better scalability.

What is a partition in the context of NoSQL databases?

In NoSQL databases, a partition refers to a part of the database that is managed by a single server, helping to distribute the workload across multiple servers.

How does a NoSQL database determine where to store an item?

A NoSQL database uses a hash function to convert an item's primary key into a number that falls within a certain range, which then determines the partition or server where the item will be stored.

What is a keyspace in the context of NoSQL databases?

A keyspace is the range of numbers generated by the hash function, which is used to determine the distribution of data across different partitions or servers in a NoSQL database.

How does the schemaless nature of NoSQL databases provide an advantage?

The schemaless nature allows items in the database to have different structures, providing flexibility and making it easier to adapt to evolving application and data structures without the risk of data loss.

What is the trade-off when using NoSQL databases for data retrieval?

NoSQL databases are optimized for retrieving data by primary key, making operations like finding all orders above a certain amount inefficient compared to relational databases that can handle complex queries more effectively.

What does 'eventually consistent' mean in the context of NoSQL databases?

Eventual consistency means that after writing a new item to the database, it might not immediately be available when read back due to the replication process across multiple servers, although this is typically resolved within milliseconds.

Why are both NoSQL and relational databases expected to coexist?

Both NoSQL and relational databases have their own strengths and weaknesses, and they are suited to different types of data and use cases, which is why they are expected to coexist in the foreseeable future.

Can you name some popular NoSQL databases provided by cloud providers?

AWS offers DynamoDB, Google Cloud offers BigTable, and Azure offers CosmosDB, which are all examples of NoSQL databases provided by major cloud providers.

What is the significance of the name 'NoSQL' and how can it be interpreted?

The name 'NoSQL' can be interpreted as 'not only SQL', indicating that some NoSQL databases have partial SQL query language understanding, and 'non-relational', highlighting their inability to easily store relational data.