Blog MongoDB vs PostgreSQL: Choosing the Right Database For Your Needs

MongoDB vs PostgreSQL: Choosing the Right Database For Your Needs

MongoDB vs PostgreSQL Compared


In the realm of modern data management, choosing the right database system is critical for efficient and effective handling of information. Two prominent contenders in this arena are MongoDB and PostgreSQL. MongoDB, a NoSQL database, and PostgreSQL, an open-source relational database, each offer distinct advantages and trade-offs. This comprehensive comparison delves into the key features, use cases, performance, scalability, and data models of MongoDB and PostgreSQL, aiding in the decision-making process for selecting the appropriate database solution.

Overview – MongoDB vs. PostgreSQL

What is MongoDB?

MongoDB, classified as a NoSQL database, belongs to the category of document databases. It is designed to store, manage, and retrieve data in flexible and schema-less documents. MongoDB uses BSON (Binary JSON) format to store data, which is more intuitive for developers and allows them to store varying structures within a collection. This approach lends itself well to handling unstructured or semi-structured data, making MongoDB an ideal choice for applications requiring agility and fast iterations.

What is PostgreSQL

PostgreSQL is a widely used relational database management system (RDBMS). It follows a structured model where data is organized into tables with defined schemas. This traditional approach is suited for applications that demand strict data integrity, complex queries, and relationships between data entities.

Key Feature Comparison – MongoDB vs. PostgreSQL

How Data is Stored

MongoDB provides a flexible schema-less model where documents within collections can have varying structures, allowing for seamless evolution of the data model. MongoDB also provides tunable levels of ACID (Atomicity, Consistency, Isolation, Durability) compliance depending on the configuration, but full ACID compliance can impact performance. MongoDB is built on the principles of CAP Theorem which focuses on Consistency, Availability, and Partition. Unlike the ACID properties of SQL databases, CAP theorem focuses on availability of data.

PostgreSQL was built on a fixed schema model, necessitating predefined table structures and data types. PostgreSQL, like other relational databases, require primary and foreign keys to be defined which essentially map relationships between different tables. Changes in the schema often require migrations, which can be more complex. PostgreSQL also offers strong ACID compliance out-of-the-box, making it suitable for applications demanding strict data consistency and integrity. Generally, SQL databases offer high data consistency and integrity whereas MongoDB offers high availability of data.

Performance and Scalability

MongoDB is known for horizontal scalability. MongoDB’s sharding enables distribution of data across multiple servers. This feature suits applications requiring massive amounts of data and high throughput. Its performance may degrade when ACID compliance is heavily emphasized.

Vertical scaling is best with PostgreSQL, where performance is enhanced by upgrading hardware or optimizing queries. PostgreSQL’s vertical scalability and focus on ACID compliance make it suitable for scenarios demanding strict data integrity and complex queries. Its performance scales well vertically with hardware upgrades, but horizontal scaling might require more intricate setup. While it supports some level of horizontal scaling, it’s not as ideal for this structure in comparison with MongoDB.

Use Cases and Suitability

MongoDB is suited for use cases such as real-time applications where rapid updates and flexible schema are crucial. Applications like social media platforms, content management systems, e-commerce sites, and Internet of Things (IoT) applications are all examples of where MongoDB shines due its the ability to store diverse data in varying formats.

PostgreSQL shines when storing data from applications with complex data relationships that require sophisticated queries and joins, such as financial systems, data warehousing, and CRM solutions. Projects with stringent regulatory requirements due to PostgreSQL’s robust ACID compliance. Situations where data consistency and referential integrity are paramount.

Querying – MQL vs SQL

MongoDB uses MongoDB Query Language (MQL), while PostgreSQL uses SQL. Each one is very different in syntax and best suited for the structure in which their data is stored. MQL is great for query efficiency, performance, and scalability parsing through a large amount of data. Its drawbacks are that it isn’t suited for joining between documents and uses a large amount of memory. SQL is great for joining between tables and is a standardized language that many are familiar with. With large amounts of data, queries can take a long time to run. See this MongoDB guide on SQL vs MQL keyword mappings.

MongoDB vs PostgreSQL Compared:

How Data is Stored– Flexible schema-less model
– Documents can have varying structures
– Tunable ACID compliance
– Focuses on CAP Theorem (Consistency, Availability, Partition)
– Fixed schema model
– Requires predefined table structures and data types
– Requires primary and foreign keys
– Strong ACID compliance
Performance and Scalability– Known for horizontal scalability
– Uses sharding for data distribution
– Performance may degrade with high ACID compliance
– Best with vertical scaling
– Enhanced performance with hardware upgrades
– Supports some horizontal scaling but not as ideal as MongoDB
Use Cases and Suitability– Real-time applications
– Social media platforms
– Content management systems
– E-commerce sites
– IoT applications
– Applications with complex data relationships
– Financial systems
– Data warehousing
– CRM solutions
– Projects with stringent regulatory requirements
Querying– Uses MongoDB Query Language (MQL)
– Efficient, performant, and scalable
– Not suited for joins
– Uses a large amount of memory
– Uses SQL
– Great for joining between tables
– Standardized and familiar
– Can be slow with large amounts of data

Knowi and MongoDB

See how easy it is to connect and query MongoDB using Knowi. No connectors or additional applications required. 

MongoDB and Knowi

Knowi and PostgreSQL

Connecting to and querying PostgreSQL is just as easy as MongoDB (as shown above). Just enter your connection credentials and query away.

PostgreSQL and Knowi

Interested in learning more about Knowi? Schedule a short demo call with us!


Choosing between MongoDB and PostgreSQL depends on the specific data requirements and expertise of your team. MongoDB shines in scenarios where flexibility, agility, and unstructured data storage are essential. PostgreSQL excels in applications demanding complex queries, data integrity, and structured data relationships.

As technology evolves, some lines between the two databases blur, with MongoDB introducing more structured features and PostgreSQL adopting NoSQL-like functionalities. In the end, understanding the unique needs of the project and aligning them with the strengths of each database will lead to the most suitable choice.

For information on MongoDB vs SQL generally, see our blog post MongoDB Vs SQL.

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