In the world of API design, three main architectural approaches have emerged as popular options: SOAP, REST, and gRPC. But what exactly is the difference between these three? With continuous evolution in API technology, it’s important to understand how these architectures compare in 2024 based on modern application requirements and development trends.
SOAP: The Old Standard
SOAP (Simple Object Access Protocol) has been around since the late 1990s and became popular as a standard approach for exchanging structured information between web services.
How SOAP Works
At its core, SOAP relies on XML to provide a messaging framework. All data sent via SOAP is transmitted in XML format. This allows for standardized and structured communication between applications.
Some key things to know about how SOAP operates:
- Use of WSDL: SOAP services expose their capabilities through a WSDL (Web Services Description Language) file. This file defines things like endpoints, operations, input and output formats.
- Heavy focus on schemas: SOAP places a heavy emphasis on schemas as part of its XML data exchange format. This allows for robust data validation.
- Use of protocols like HTTP and SMTP: Although XML defines the data layer, SOAP services still rely on standard internet protocols like HTTP and SMTP for message transmission.
As one of the older standards, SOAP emerged at a time when legacy languages and systems still relied heavily on XML. As a result, it has some advantages that aligned well with older infrastructure:
- Language agnostic: The XML format allows SOAP services to work across many languages.
- Standardized: SOAP is an open standard that has been widely adopted. This avoids vendor lock-in.
- Robust validation: The required schemas enable strong validation of data inputs and outputs.
However, as development practices have evolved, SOAP has shown some distinct disadvantages…
REST: The Lightweight Alternative
How REST Works
REST relies on simple HTTP requests between client and server. Data is sent in lightweight formats like JSON rather than complex SOAP envelopes.
Here is how it differs from SOAP:
- No required XML: REST can handle simple text, JSON, XML, and other formats.
- No required WSDL descriptor: While REST APIs often have a Swagger/OpenAPI description, there is no requirement for a standardized file.
- Leverages HTTP verbs and status codes: REST uses the native HTTP protocol for core functionality like GET, POST, PUT, DELETE requests.
As you can see, REST aimed to simplify some of the overhead that added complexity to SOAP implementations:
- Lightweight: Without the XML bloat, REST messages require less bandwidth.
- Flexible: Various data formats are supported beyond just XML.
- Aligns with web: The use of core HTTP protocols aligned well with growth of the web.
However, as API usage has scaled dramatically, REST has also shown limitations for some modern use cases…
gRPC: High Performance APIs
gRPC is one of the newest architectural approaches, emerging in 2015. Created by Google, it aims to combine the best aspects of REST and SOAP while optimizing for performance and efficiency at scale.
How gRPC Works
Like REST, gRPC leverage HTTP/2 as a transport layer and utilizes Protocol Buffers for message formatting. However, it diverges with its support for things like:
- Strict schema contracts: Schemas are required like SOAP but use a lightweight Protobuf format.
- Binary messaging: Protobuf serializes data into high performance binary messages.
- Bidirectional streams: gRPC natively supports async request/response streams.
As Google built gRPC for its own internal systems, it architected the technology with modern infrastructure in mind:
- High throughput: Benchmark tests show gRPC can handle 500k requests per second per core.
- Low latency: The binary Protobuf format allows for low overhead data transfer compared to JSON or XML.
- Bi-directional streams: Native support for asynchronous full duplex communications between client/server.
Now that we’ve covered the basics of each option, let’s directly compare them across a few key factors:
SOAP vs REST vs gRPC: Key Comparison
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As we can see, each option has its own strengths and weaknesses that lend itself to different use cases.
Key Considerations by Use Case
When evaluating SOAP vs REST vs gRPC in 2024, there are a few key criteria to consider that can help determine the best architectural fit:
Use Case #1: External Partner Integrations
For B2B app integrations involving external partners, SOAP may still provide the most standardized approach, avoiding vendor lock-in thanks to open schemas and common transports.
Use Case #2: Public APIs and Microservices
For more flexible public APIs and internal microservices, REST remains a solid default choice due to its simplicity, ubiquity, and alignment with web protocols.
Use Case #3: High-Performance Internal Systems
However, for high scale internal systems that demand maximum throughput and minimal latency, gRPC delivers best in class performance and efficiency. Its use is growing for core infrastructure.
The Path Forward: API Polyglot
Given the continued demand for services across the spectrum of performance, scale, and external compatibility requirements, many organizations are adopting an API polyglot approach for their architectures:
- SOAP for legacy systems and external integrations
- REST for broad external APIs and mobile apps
- gRPC for high-performance inter service communications
This hybrid model allows tapping the right tool for each specific job. In 2024 and beyond, being fluent across SOAP, REST, and gRPC will enable architects to build robust and resilient architectures.
When it comes to choosing web service architectures, SOAP, REST and gRPC each have their own strengths and weaknesses. SOAP offers standardization and robustness but at the cost of complexity. REST provides simplicity and flexibility aligned with web protocols. And gRPC delivers maximum high performance scalability leveraging modern infrastructures.
As API usage continues to accelerate, the right answer is often an API polyglot strategy combining multiple architectures for different use cases rather than taking a one size fits all approach. By understanding these core API paradigms in depth, architects can deliver systems optimized for productivity, performance and resilience.
What is the main difference between SOAP and REST?
The main difference is that SOAP relies on XML messaging while REST utilizes simpler HTTP requests and lightweight data formats like JSON.
Is gRPC only for internal communications?
While gRPC is commonly used for high performance internal systems, it also works well for public APIs needing scalability, speed and efficiency.
What transport protocols do they each use?
SOAP services can leverage HTTP, SMTP and more. REST is focused on core HTTP/HTTPS protocols. gRPC utilizes HTTP/2 specifically.
Is SOAP outdated technology?
While SOAP is the oldest approach, it still has relevance for standardized integrations with legacy systems and external partners.
What is the main advantage of gRPC over REST?
gRPC has significant performance benefits over REST benchmark tests show it handles 500k requests per second per core vs. around 35k for REST.
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