sequelize is a promise-based Node.js ORM (Object-Relational Mapping) library that provides an easy way to interact with relational databases such as PostgreSQL, MySQL, MariaDB, SQLite, and Microsoft SQL Server. It allows developers to define models, manage relationships, and perform CRUD operations in a more intuitive and organized manner. While Sequelize is a popular choice for ORM in Node.js applications, there are several alternatives worth considering:

• bookshelf is an ORM for Node.js that is built on top of the Knex.js SQL query builder. It provides a simple and flexible way to work with relational databases, allowing developers to define models and relationships easily. Bookshelf supports features like eager loading, virtuals, and pagination, making it a good choice for applications that require a lightweight ORM with a focus on simplicity and flexibility. If you are already using Knex.js for database queries, Bookshelf can be a natural fit.
• knex is a SQL query builder for Node.js that provides a powerful and flexible way to build and execute SQL queries. While not an ORM in the traditional sense, Knex allows developers to write SQL queries in a programmatic way, making it easier to work with databases. It supports multiple database engines and provides features like migrations and seed management. If you prefer to have more control over your SQL queries and do not need the full abstraction of an ORM, Knex is a great choice.
• mongoose is an ODM (Object Data Modeling) library for MongoDB and Node.js. It provides a schema-based solution to model application data, allowing developers to define schemas and interact with MongoDB in a more structured way. Mongoose is ideal for applications that use MongoDB as their database and require features such as validation, middleware, and population of related documents. If your project is focused on MongoDB, Mongoose is the go-to solution.
• typeorm is an ORM for TypeScript and JavaScript that works with various databases, including MySQL, PostgreSQL, MariaDB, SQLite, and more. It supports both Active Record and Data Mapper patterns, giving developers the flexibility to choose their preferred approach. TypeORM is particularly well-suited for TypeScript projects, as it leverages TypeScript's features for type safety and decorators. If you are working in a TypeScript environment and need a robust ORM, TypeORM is an excellent option.

To see how Sequelize compares with Bookshelf, Knex, Mongoose, and TypeORM, check out the comparison: Comparing bookshelf vs knex vs mongoose vs sequelize vs typeorm.