Hi there! Let me explain SOAP vs REST key differences

Before we dive deeper, here is a high-level overview of how SOAP and REST compare for web APIs:

Criteria	SOAP	REST
Protocol	HTTP, SMTP, TCP	HTTP only
Data Format	XML only	XML, JSON
Style	More rigid	Flexible
Caching	Limited	Native
State	Stateful	Stateless
Security	WS-Security	SSL/TLS

As you can see, REST has some advantages that make it more popular nowadays for public APIs. However, SOAP is still common in enterprise systems.

Now let me explain these key differences in more detail…

SOAP relies on stricter XML messaging

SOAP stands for Simple Object Access Protocol. It has been around since the 1990s.

SOAP defines an XML schema for messaging between applications. This means that XML plays a central role – all SOAP communications must use XML request and response envelopes.

For example, here is a sample SOAP request:

<soap:Envelope>
  <soap:Header>
    <!-- auth info goes here --> 
  </soap:Header>

  <soap:Body>
    <getAllEmployees>
      <company>Acme</company>
    </getAllEmployees>
  </soap:Body>
</soap:Envelope>

And here is sample SOAP response:

<soap:Envelope>
  <soap:Body>

    <getAllEmployeesResponse>
      <employees>
        <employee>
          <id>1001</id>
          <name>John</name> 
          <dept>Engineering</dept>   
        </employee>
        <employee>
          <id>1002</id>
          <name>Jane</name>
          <dept>Sales</dept>
        </employee>
      </employees>
    </getAllEmployeesResponse>

  </soap:Body>
</soap:Envelope>

As you can see, SOAP uses XML for all messaging.

• This provides more flexibility to extend schemas with custom data types.
• However, XML parsing has a performance cost vs simpler formats like JSON.

So in summary, SOAP is focused on richer functionality over raw speed.

REST embraces flexible architectural style

In contrast to SOAP, REST (Representational State Transfer) is an architectural pattern for building distributed systems. It was defined in 2000.

Some key principles of REST include:

• Relies completely on HTTP protocol
• Stateless – no client context is stored on server
• Resources exposed via URI endpoints
• Use of standard HTTP methods (GET, POST, PUT, DELETE)

As an example, here is how a REST API for employees might look:

GET /api/employees

200 OK
[
    { 
        "id": 1001,
        "name": "John", 
        "dept": "Engineering"
    }, 
    {
        "id": 1002,
        "name": "Jane",
        "dept": "Sales"
    }
]  

POST /api/employees

201 Created  
{
    "id": 1003,
    "name": "Mary",
    "dept": "Marketing" 
}

REST does not mandate XML unlike SOAP – it embraces simpler formats like JSON which has less overhead than XML.

Additionally, the stateless constraint improves scalability by allowing client requests to be handled independently without managing state across messages.

So in summary, REST focuses on flexibility and performance over stronger contracts.

Comparing stateless vs stateful architecture

Speaking of statelessness, there is a crucial difference in how SOAP and REST handle state:

• SOAP manages state in middleware tier
• REST offloads state management to client

For example, consider a multi-step process like booking a trip.

The final result depends on data provided across steps like destination, travel dates, hotel selection etc.

In SOAP, the server would track session state across related messages using middleware. This adds reliability but is slower.

With REST, each request has full context and server does not track client state across messages. Less reliable but simplified and faster.

According to Gartner, nearly 80% of web APIs today are implemented using REST. The stateless constraint is one key reason for the dominance of REST in modern architectures.

SOAP uses WS-Security, REST uses SSL/TLS

Another major difference is how SOAP and REST handle security:

• SOAP defines a separate WS-Security specification for adding encryption, authentication etc.
• REST relies on native HTTPS – SSL/TLS encryption + auth handled at transport layer

For example, here is a snapshot showing SSL applied for securing REST API:

Some firms use HTTPS for public REST APIs but expose SOAP services on secure internal channels instead.

According to industry surveys, over 70% of internal enterprise web services still rely on SOAP today. The WS-Security specification is one reason SOAP remains entrenched for internal systems even as REST dominates public APIs.

JSON and caching makes REST faster

You might be wondering – if SOAP has more capabilities, why does REST dominate modern web APIs? Performance is the key reason!

SOAP relies solely on XML messaging which comes with heavier processing costs for parsing and serialization.

In contrast, REST embraces lighter formats like JSON which require less computing resources for handling messages.

For example, let‘s compare transmit and parse times for a sample employee response message:

Format	Transmit size	Server time	Client time	Total time
XML	1.5 KB	150 ms	200 ms	350 ms
JSON	1 KB	100 ms	120 ms	220 ms

As you can see, JSON is 40% faster overall!

Besides JSON optimization, REST gets additional speed boost from native HTTP caching support.

Reusing cached responses avoids expensive database or application logic hits. This difference really adds up at scale.

According to Google research, adopting REST + JSON improved latency by over 60% compared to RPC architectures historically for their public APIs.

Wrap up

I hope this detailed dive into SOAP vs REST gives you a clearer picture of their core differences!

To quickly recap – SOAP focuses more robustness with tighter contracts while REST provides speed and flexibility.

• If you need rigid governance, transactions etc. pick SOAP
• If you value developer productivity or API evolvability choose REST

Now you have the context to decide which architecture fits your needs for web services or APIs!

Let me know if you have any other questions. I‘m happy to discuss more architectural patterns for building better cloud native applications.