A Comprehensive Comparison of Database-to-API Frameworks

In the world of modern application development, one challenge consistently surfaces: how to quickly and efficiently expose database operations through RESTful APIs. Two powerful open-source solutions tackle this problem from different angles: PostgREST for PostgreSQL and RESTHeart for MongoDB. While they share a common philosophy of automatic API generation, they serve distinct database ecosystems and offer unique architectural approaches.

The Core Philosophy: Database-First Development

Both PostgREST and RESTHeart embrace a "database-first" philosophy that fundamentally differs from traditional API development approaches. Instead of writing controllers, routes, and data access layers manually, both frameworks treat the database schema itself as the single source of truth. This approach eliminates the impedance mismatch between your data model and your API, reduces boilerplate code, and ensures that your API always reflects your current database structure.

The key insight driving both projects is that most CRUD operations don’t require custom business logic. By delegating these repetitive tasks to a specialized layer that understands your database, you can focus on implementing the features that make your application unique.

PostgREST: Turning PostgreSQL into a REST API

PostgREST is a standalone web server written in Haskell that automatically generates a RESTful API from any PostgreSQL database. Simply point it at your database, and it introspects the schema to create corresponding HTTP endpoints.

Core Capabilities

PostgREST offers comprehensive database operations through HTTP verbs. Standard CRUD operations map naturally to GET, POST, PUT, PATCH, and DELETE requests. The framework supports complex queries through URL parameters, allowing filtering, sorting, pagination, and even joins without writing a single line of backend code.

For example, querying with filters looks like this:

GET /students?age=gt.18&order=name.asc&limit=10

PostgREST translates these URL parameters directly into optimized PostgreSQL queries, leveraging the database’s query planner for maximum performance.

Security Model

One of PostgREST’s most compelling features is how it handles security. Rather than implementing authorization logic in the API layer, PostgREST leverages PostgreSQL’s role-based access control system. When a request arrives with JWT credentials, PostgREST assumes the corresponding PostgreSQL role for that connection, ensuring the database itself enforces all permissions.

This approach provides several advantages. You define security rules once in the database using standard SQL GRANT statements and Row-Level Security policies. There’s no application-layer code that could bypass database constraints. Security becomes declarative and centralized, making it easier to audit and maintain.

Architecture and Performance

Built on Haskell and the Warp HTTP server, PostgREST benefits from a highly efficient compiled language. It uses connection pooling through the Hasql library and PostgreSQL’s binary protocol to minimize serialization overhead. The framework delegates as much work as possible to PostgreSQL itself, including JSON serialization, data validation, and authorization checks.

This design results in exceptional performance. Teams have reported dramatic improvements when migrating from traditional ORM-based APIs, with some seeing 10x speed increases and massive reductions in memory usage compared to their previous implementations.

API Versioning and Documentation

PostgREST handles API versioning elegantly through PostgreSQL schemas. You can expose different versions of your API by creating separate schemas with different views on the underlying tables. This allows you to evolve your data model without breaking existing clients.

The framework automatically generates OpenAPI specifications for your API, which can be rendered with tools like Swagger UI for interactive documentation. This means your API documentation is always in sync with your actual database structure.

Limitations and Considerations

PostgREST deliberately maintains a focused scope. It excels at CRUD operations but leaves concerns like sending emails, complex business logic, or integration with external services to other tools. You’ll need to combine PostgREST with additional components (like Nginx for routing, custom PostgreSQL functions for complex operations, or separate microservices for non-CRUD functionality) to build complete applications.

There’s also no native GUI for managing configurations, and while the API documentation can be generated from the OpenAPI spec, this requires additional setup.

RESTHeart: The MongoDB Backend Framework

RESTHeart takes a broader approach as a full-featured Java backend framework that provides instant REST, GraphQL, and WebSocket APIs for MongoDB. While PostgREST focuses narrowly on REST operations, RESTHeart positions itself as a comprehensive application framework.

Multi-Protocol Support

Unlike PostgREST’s REST-only approach, RESTHeart natively supports three different protocols for accessing MongoDB data. The REST API provides the same automatic CRUD operations you’d expect, with support for filtering, pagination, sorting, and aggregations. The GraphQL API allows you to define schemas and queries through configuration rather than code. The WebSocket API enables real-time updates and change streams, notifying clients when data changes without requiring polling.

"Query": {
"countPostsByCategory": {
"db": "restheart",
"collection": "users",
"stages": [
{ "$group": { "_id": "$category", "count": { "$count": {} }}
]
}
}

This multi-protocol design makes RESTHeart particularly well-suited for modern applications that need real-time features alongside traditional request-response patterns.

Extensibility Through Plugins

RESTHeart’s plugin architecture distinguishes it from PostgREST’s minimalist approach. The framework provides four plugin types: Services (custom endpoints), Interceptors (request/response transformers), Providers (dependency injection), and Initializers (startup tasks).

Plugins can be written in Java, Kotlin, JavaScript, or TypeScript, giving teams flexibility in their technology choices. The restheart-core runtime handles plugin loading, configuration parsing, security enforcement, and request routing. Pre-built plugins for MongoDB operations, GraphQL support, and security come bundled with the distribution.

@RegisterPlugin(
name = "kotlinGreeterService",
defaultURI = "/greetings",
description = "just another Hello World in Kotlin")
class GreeterService : JsonService {
override fun handle(req: JsonRequest, res: JsonResponse) {
when(req.method) {
METHOD.GET -> res.content = obj().put("msg", "Hello World").get()
METHOD.OPTIONS -> handleOptions(req);
else -> res.setStatusCode(HttpStatus.SC_METHOD_NOT_ALLOWED);
}
}
}

This architecture allows RESTHeart to grow with your application. You can start with zero-code APIs and progressively add custom logic through plugins as requirements evolve.

Security and Authentication

RESTHeart includes comprehensive authentication and authorization features out of the box. Multiple authentication mechanisms are supported, including JWT, Basic Auth, and custom authenticators. Authorization can be configured through Access Control Lists with fine-grained permissions, integration with MongoDB roles, and request predicates for conditional access.

{
"_id": "userCanGetOwnCollection",
"roles": ["user"],
"predicate": "method(GET) and path-template('/{userid}') and equals(@user._id, ${userid}) and qparams-contain(page) and qparams-blacklist(filter, sort)",
"priority": 100,
"mongo": {
"readFilter": { "_$or": [{ "status": "public" }, { "author": "@user._id" }] },
"projectResponse": { "log": 0 }
}
}

User and permission management happens directly in MongoDB collections, eliminating the need for separate user databases or authentication services. This streamlined approach significantly reduces development time for applications with standard security requirements.

Performance and Deployment

Built on Undertow (the web server powering Red Hat’s WildFly applpication server) and fully embracing Java 21’s virtual threads, RESTHeart achieves impressive performance characteristics. Virtual threads enable efficient handling of thousands of concurrent connections without the complexity of traditional async programming.

The framework starts in approximately 100 milliseconds and has a small memory footprint (around 10MB for the JAR, 50MB when compiled to native). Each request runs in its own dedicated thread, making code simple and thread-safe by default.

RESTHeart supports multiple deployment options: as a standalone JAR, as a Docker container, compiled to a GraalVM native binary, or through RESTHeart Cloud (a fully managed service). The stateless architecture enables horizontal scaling across multiple instances.

MongoDB Feature Coverage

RESTHeart exposes MongoDB’s full capabilities through its APIs. This includes advanced features like aggregation pipelines, transactions (when MongoDB runs as a replica set), GridFS for binary file storage, schema validation, indexes, and even change streams for real-time data.

The framework works not just with MongoDB but also with compatible databases like FerretDB (which provides MongoDB compatibility for PostgreSQL), AWS DocumentDB, and Azure Cosmos DB.

License Considerations

RESTHeart uses dual licensing: AGPL for open-source use and a Business Friendly Enterprise License for commercial applications. The AGPL version has no feature restrictions, but organizations building closed-source products typically need the Enterprise License.

Key Similarities

Despite targeting different databases, PostgREST and RESTHeart share several fundamental characteristics:

✅ Zero-Code Data APIs: Both eliminate the need to manually code CRUD endpoints, automatically generating APIs from database schemas.

✅ Database-Centric Security: Both leverage the database’s native security features rather than implementing authorization in application code.

✅ Declarative Configuration: Most functionality comes from database schema and simple configuration rather than imperative programming.

✅ Performance Focus: Both achieve high throughput by delegating work to the database and using efficient underlying technologies.

✅ Open Source with Commercial Options: Both offer open-source licenses with commercial support options available.

Key Differences

Database Targets

The most obvious difference is database compatibility. PostgREST exclusively supports PostgreSQL (and must support its wire protocol). RESTHeart targets MongoDB and MongoDB-compatible databases. This isn’t just a connection string change; it reflects fundamentally different data models (relational vs. document-oriented) with distinct query capabilities, transaction semantics, and schema approaches.

Architectural Scope

PostgREST maintains a deliberately narrow focus on REST API generation. It does one thing extremely well and expects you to combine it with other tools for additional functionality. This Unix philosophy approach provides simplicity and composability.

RESTHeart takes a framework approach, providing a broader set of built-in features including multiple API protocols, plugin systems, and application-level functionality. It aims to be a complete backend platform rather than just an API gateway.

Programming Languages and Ecosystem

PostgREST is written in Haskell, leveraging functional programming concepts and the Warp server’s efficiency. While you don’t need to know Haskell to use it, extending PostgREST typically means writing PostgreSQL functions and using other ecosystem tools.

RESTHeart runs on the JVM, is written in Java, and supports plugin development in Java, Kotlin, JavaScript, and TypeScript. This aligns with the extensive Java enterprise ecosystem and makes it more approachable for teams already working in these languages.

Security Implementation

Both emphasize database-native security, but the implementations differ. PostgREST’s JWT-to-PostgreSQL-role mapping creates a direct connection between authentication tokens and database permissions. Every request runs under a specific PostgreSQL role with its associated privileges.

RESTHeart provides a more traditional security layer with built-in authentication mechanisms and ACL-based authorization, while also supporting MongoDB role integration. This offers more flexibility but adds a security layer between clients and the database.

API Protocols

PostgREST focuses exclusively on REST over HTTP, generating endpoints that follow RESTful conventions. RESTHeart supports REST, GraphQL (with configurable schemas), and WebSockets for real-time updates, providing more options for client applications with different requirements.

Extension Models

PostgREST’s extension points are primarily PostgreSQL functions and views, combined with external tools handling concerns outside CRUD operations. This keeps the core simple but requires architectural planning.

RESTHeart’s plugin system provides formalized extension points with Java/JavaScript code, dependency injection, and lifecycle management. This makes adding custom business logic more straightforward within the framework itself.

Use Case Recommendations

Choose PostgREST When You

• Have an existing or planned PostgreSQL database
• Need a lightweight, focused REST API layer
• Want to leverage PostgreSQL’s advanced features (foreign keys, complex queries, stored procedures)
• Prefer a minimalist architecture with composable tools
• Have strong SQL skills and want database-driven development
• Value the simplicity of having security defined entirely in the database
• Don’t need GraphQL or WebSocket support
• Can handle additional concerns (email, file storage, etc.) through other services

Choose RESTHeart When You

• Work with MongoDB or need a document database
• Want multiple API protocols (REST, GraphQL, WebSockets) from one backend
• Need real-time data updates through change streams
• Prefer an all-in-one framework over composing multiple tools
• Work in Java/JVM ecosystems
• Want to write custom business logic in Java, Kotlin, or JavaScript
• Need a rapid application development platform with minimal setup
• Want to progressively add complexity through plugins as requirements grow
• Require flexible schema evolution and document-oriented data modeling

Performance Considerations

Both frameworks deliver excellent performance, though measuring them directly against each other would be comparing apples to oranges given their different database targets.

PostgREST benefits from Haskell’s efficiency, PostgreSQL’s mature query planner, and aggressive delegation of work to the database. Teams report handling thousands of requests per second with minimal resource usage.

RESTHeart leverages Java virtual threads for efficient concurrency, Undertow’s high-performance HTTP handling, and MongoDB’s scalable architecture. The framework can handle hundreds of thousands of transactions per second in optimized deployments.

For most applications, the database itself will be the bottleneck rather than the API framework, making your choice of database more significant than the framework’s raw performance characteristics.

Development Experience

PostgREST Workflow

Development with PostgREST centers on your PostgreSQL schema. You design tables, create views, define functions, and set up permissions using SQL. The API emerges automatically from these definitions. Testing often happens directly in PostgreSQL before making HTTP requests.

The workflow emphasizes database skills. If you’re comfortable with SQL and relational modeling, PostgREST’s approach feels natural. If your team struggles with advanced SQL, the learning curve may be steeper.

RESTHeart Workflow

RESTHeart development typically starts with zero configuration. Connect it to MongoDB, and you can immediately start creating collections and documents through the REST API. As requirements grow, you add configuration for relationships, validation schemas, or GraphQL mappings. Eventually, you might develop custom plugins for business logic.

This progressive complexity model allows teams to start quickly and add sophistication gradually. The framework supports both low-code and code-heavy approaches depending on application requirements.

Community and Ecosystem

PostgREST has an active open-source community on GitHub with contributions from developers worldwide. The project maintains solid documentation, and its focused scope means the API surface is relatively stable. Commercial support is available through Patreon supporters and third-party consultants.

RESTHeart is developed by SoftInstigate, which provides both open-source AGPL licensing and commercial enterprise licensing with professional support. The project has comprehensive documentation, tutorials, and example applications. The commercial backing provides long-term stability and professional support options.

Migration and Integration

Integrating PostgREST

PostgREST integrates well with existing PostgreSQL databases. You can start with a read-only API by creating views and gradually expand to write operations. The framework works alongside traditional applications, making incremental adoption feasible.

Common integration patterns include using Nginx as a reverse proxy for routing, combining PostgREST with other microservices for non-CRUD operations, and leveraging PostgreSQL NOTIFY/LISTEN for real-time features through external tools.

Integrating RESTHeart

RESTHeart can connect to existing MongoDB deployments without schema modifications. Since MongoDB is schema-less, you can immediately expose existing collections through the API with automatic CRUD operations.

The framework’s plugin system facilitates integration with existing Java applications, and the multi-protocol support makes it easier to serve different client types (web, mobile, real-time) from a single backend.

Conclusion

PostgREST and RESTHeart represent mature, production-ready approaches to automatic API generation, each tailored to its respective database ecosystem. They share a vision of database-first development that eliminates boilerplate code and embraces declarative data modeling.

PostgREST’s minimalist, focused approach makes it ideal for teams comfortable with PostgreSQL who want a lightweight API layer that leverages the database’s full power. Its Unix philosophy of doing one thing well, combined with PostgreSQL’s robustness, creates a compelling platform for data-centric applications.

RESTHeart’s comprehensive framework approach provides everything needed for MongoDB-based applications out of the box. The multi-protocol support, plugin architecture, and progressive complexity model make it excellent for teams wanting rapid development without sacrificing the ability to add custom logic when needed.

Your choice between them primarily depends on your database selection, which itself should be driven by your data model, query patterns, and scalability requirements. If you need PostgreSQL’s relational capabilities, ACID guarantees, and SQL power, PostgREST is the clear choice. If MongoDB’s document model, flexible schema, and horizontal scalability fit your needs, RESTHeart provides an exceptional backend platform.

Both projects prove that the tedious work of building CRUD APIs can be automated, freeing developers to focus on what makes their applications unique. In a world where time-to-market and developer productivity are critical, these frameworks represent a significant evolution in how we build data-driven applications.

Resources

PostgREST

• Documentation: https://postgrest.org/
• GitHub: https://github.com/PostgREST/postgrest
• License: MIT

RESTHeart

• Documentation: https://restheart.org/docs/
• GitHub: https://github.com/SoftInstigate/restheart
• License: AGPL / Enterprise (dual license)
• Commercial: https://cloud.restheart.com/