Stateful vs. Stateless: Understanding the Key Differences

Stateless and stateful protocols are fundamentally different from each other. A stateless system sends a request to the server and relays the response (or the state) back without storing any information. On the other hand, stateful systems expect a response, track information, and resend the request if no response is received. This article discusses the 10 key differences between stateful and stateless protocols, architecture, or applications, along with two similarities. 

Stateful vs. Stateless 

The internet and everything it is used for are all controlled by protocols – i.e., rules and guidelines that direct every data sent across the internet. Network protocols are broadly grouped into the stateful and stateless structures, which we will now delve into. 

What is stateful architecture?

Stateful architecture or application describes a structure that allows users to store, record, and return to already established information and processes over the internet. It entails transactions that are performed using past transactions as a reference point. In stateful applications, the current transaction can be affected by the previous ones. 

Because of this, a stateful application uses the same server to process its requests. Stateful transactions can be likened to an ongoing discussion with statements made based on already established facts. In stateful transactions, you can pick up from wherever in situations where there is an incomplete transaction.

A stateful application maintains the state of every session irrespective of the importance. Stateful architecture is used as a foundation for several existing technologies today. The File Transfer Protocol (FTP) and the Telnet were good examples of stateful architecture. Some very vital applications that use stateful architecture are online banking and email. The key advantages of the stateful concept are as follows:

• The stateful protocol can deliver better performance because it stores information that helps future transactions.
• Stateful architecture has an excellent extra security layer, making it very popular in the banking and finance sector for online transactions.
• Stateful protocols are intuitive due to their ‘memory.’

There are also a few downsides one should note:

• Memory must be included as part of the server architecture for data storage. 
• The server bears a considerable burden on the functionality of the entire application, so stateful applications need an intricate server.
• Performance is partly dependent on the efficiency of the network memory. This means continuous management throughout the time the service is being offered. 

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What is stateless architecture?

A stateless architecture or application is a type of Internet protocol where the state of the previous transactions is neither stored nor referenced in subsequent transactions. Each request sent between the sender and receiver can be interpreted and does not need earlier requests for its execution. This is a protocol where a client and server request and response are made in a current state. In addition, the status of the current session is not retained or carried over to the next transaction. 

Stateless applications manage short-term requests using print servers and a Content Delivery Network (CDN). An excellent example of stateless protocol at work is in the sending of an SMS. Examples of stateless protocols include Hypertext Transfer Protocol (HTTP), Domain Name System (DNS), etc. The key advantages of the stateless concept are as follows:

• Stateless protocols can bounce back rapidly in the event of system malfunction as no state is maintained or needs to be preserved. 
• It minimizes the number of resources, including storage, that would be otherwise needed to maintain transactions.
• Stateless architecture can be easily scaled up or down, as the case may be while retaining functionality.

There are also a few downsides one should note:

• Network performance may reduce because of the large amount of data sent out repetitively.
• Stateless architecture is less capable of carrying out some functions due to a lack of information storage. 

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Key Comparisons Between Stateless and Stateful 

Stateful and stateless protocols are part of our everyday use of the internet. Yet they exist as different architectures and are used in different applications. This is because of the differences between the two protocols: 

1. Saving information on servers 

When comparing stateless and stateful protocols and the architecture on which they are built, the most glaring difference is how both protocols handle data. For the stateless protocol, storing data is not a priority. Therefore, the servers used as part of the network’s infrastructure do not have to be built to store large amounts of information. 

In stateless protocols, data is not transient and does not have to be stored permanently on the servers. The bulk of the responsibility for saving information lies on the client, storing data as a cache. Also, restarting the server simply means starting a new operation with no significant data loss.

On the other hand, stateful applications depend on a server capable of storing large amounts of information. It can be pretty complex to manage the entire life cycle of an application that uses the stateful protocol. The administrators must also ensure that the proper backing storage is used. The stateful protocol requires servers to save the information of an ongoing transaction as it can be referenced in future transactions. 

2. Ease of implementation 

When considering protocols used in the internet and the world of data exchange, some are easier to implement than others. The same also applies to the broad classes of stateful and stateless protocols. Stateless protocols require lesser logical reasoning, lesser storage, and lesser queries to determine the nature of the request. This means that stateless applications often require less computer processing power and are, therefore, easier to implement.

Stateful protocols are different from stateless in this regard because a stateful application runs on more computer brain power and storage requirements than stateless. Stateful protocols are logically heavy and more challenging to implement than stateless. 

3. Client-server dependency

Computer applications generally require a two-way interface for data exchange. A phone, for example, does not browse the internet on its own except when connected to a server. It then sends requests to the server, and the server mediates this request. This principle holds for websites, applications, the cloud, databases, etc. 

However, the degree of dependency between servers and client devices varies from one protocol to another. In stateless protocols, there is little dependency between the servers and clients. Requests sent are self-contained and put less burden on the server.

However, stateful protocols retain a high level of interdependence between the server side and the clients. Requests sent to the server must be responded to before users can establish a connection. Failure of the client to get a response from a server means resending the request again. This shows how much dependency exists between clients and servers in stateful architecture. 

4. Crash and system failure management

Another difference between the stateful and stateless protocols is their response to partial or complete system failures. System failure from software or hardware components can lead to disastrous consequences when not handled properly. Even with proper handling, responding to system failure still depends on the application’s protocol. 

In stateless protocols, servers are not responsible for storing information of a session, and information exchanged in a previous transaction has little bearing on current sessions. This means that a failed server can simply be restarted after a crash with little loss of information, as there is no particular state that the system must preserve.

This contrasts sharply with the stateful protocol that stores information about previous and current sessions in a particular state. The server that is part of a stateful architecture must maintain the information of its status and details at every point. Therefore in the event of a crash, data is lost and cannot be replaced after the server is restarted, leading to data loss. 

5. Server complexity 

Previously, servers were made to handle the bulk of the processing requirements for connected devices. These devices were limited in hardware and software, letting the highly complex servers handle much of the processing and storage. Today, servers are made less complicated than they once were, which is positively fostered by the ultra-fast, high-capacity devices in use today. 

In the same way, a stateless protocol relies less on its servers and, as such, does not require highly complex servers to function. The architecture of stateless protocol makes the server design very simple.

On the other hand, stateful protocol architecture retains the method of leaving the bulk of the responsibility to the server while freeing up the client’s device. This means that servers in stateful protocol require a highly complex and heavy design.

6. Ease of scalability 

Scalability is an aspect of growth that must be considered when deciding what type of architecture to implement for any purpose. An application or website with increasing metric traffic may experience congestion and need to expand its current capacity. This usually involves adding additional services in container orchestration for cloud-based applications or servers. 

In the stateless service architecture, scaling up or down is easy and can be done automatically for cloud-based apps using an auto-scaler tool. One can add back-end servers to a front-end load balancer, and any server can easily handle requests. 

A stateful protocol has a different approach when it comes to scaling. To scale up in a stateful architecture, one must manually include additional stateful services and servers to the existing services. The same applies to scaling down a service. 

7. Speed of transaction 

Speed remains one of the top metrics considered whenever any function or service is deliberated upon in today’s world. Some applications are inherently faster than others, and while this may be multifactorial, the protocol binding the application also plays a role in the speed of transactions. 

In stateless applications, the server does not retain information on a session. In addition, it can run multiple sessions simultaneously without consulting a storage platform for more information. This enables a stateful protocol to handle incoming requests and transactions at high speed. 

Stateful routing, however, is set to make the server retain information on the transactions in sessions as long as the session lasts. This method of processing transactions gives higher control over what is being sent across and the information being passed. However, the number of transactions the server can carry out per second is reduced. This higher level of control over transactions is obtained from sacrificing the speed of day-to-day activities on the protocol. 

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8. Multitasking capabilities

Multitasking, in terms of computer technology, is the ability of a system to process multiple data inputs and produce information simultaneously. Multitasking is a result of a server being able to process multiple requests. In stateless protocol, there is no dependency on the server. Every request in itself is independent of prior transactions. This means that any resource available will be able to process the request since there is no need to access stored data.

By comparison, the opposite is true for stateful application. Every transaction in a session must be carried out using the same stateful resource or server. The server initially engaged already has the data that will be used for subsequent transactions, so one can only use it until the entire session is over.

9. Response mechanism

How devices send and respond to requests in stateless and stateful protocols also differ. For instance, in the stateless architecture, a request is made by the client to the server. Once sent, the client does not bother to know if there has been a response on the receiving side. For instance, a mobile phone does not need confirmation to send an SMS. 

Once it is sent, it does not expect a response. On the other hand, a stateful protocol requires an established connection of requests and responses for transactions to be completed. If a request is left unanswered, the request is sent again to the server. 

10. Servers specifications

In stateless architecture, the server specification can be flexible and accommodate various requests simultaneously. In the same way, a request can be processed by more than one server. This is because the information for processing the request is not tied to the server. In stateful architecture, one must use the same server to process a request already part of the transaction. This makes it different from the stateless protocol. 

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Similarities Between Stateful and Stateless Architecture 

As much as there are differences between these two protocols, they still function to the same end, data processing and information exchange on the internet. Therefore, there are some similarities between the two which include:

1. Similarities in firewall-related use cases

A firewall is a network security device that regulates and monitors traffic flow in and out of a network as guided by the organizations already set down security protocol. It is a barrier between an organization’s private network and the public network that exists as the rest of the internet. 

Firewalls were initially created as stateless protocols. Together with a standard access control list on layer 3 switches and routers, they serve to filter packets flowing between stateless networks. This was done by inspecting each packet to know the source and destination IP address enclosed on the header. If the packet is from the right source, it is allowed to pass through the firewall. 

Under the stateless protocol, this is done for each packet that comes through. Today, firewalls are also built on the stateful protocol. They don’t just track source IP address and destination IP address; they also monitor the port information using an active connection table.

Stateful firewall services inspect the data contained in a packet to ensure that the correct information is being carried. Because stateful connections store data that is used in subsequent transactions, these firewalls can recognize data in a packet as derived from a source that has already been granted permission to cross the firewall. 

A stateful firewall does this in addition to its ability to filter data packets from illegitimate networks. In this way, stateful and stateless architecture functions similarly to protect the entry of harmful or non-verified data packets from accessing the network.

2. Similarities in database-related use cases

Database systems are used by various organizations and companies of different sizes to store long-term information about their clients, activities, etc. In a stateless application, data or information about the client is not stored on the server, thus freeing up the servers to perform other functions. However, they do have a form of storing information, which is done with the help of database management systems. 

When traffic comes in through the load balancer on a network, it is directed to a server. The user then sends his request to that server. The stateless protocol generates an auth token and stores it in the database system as well as the information of the client. The token is returned to the front end, and in subsequent requests, the server can match the token with the data stored in the database. This maintains the independent state of each request as the server does not store information. 

Likewise, the stateful protocol makes use of database systems. Despite the ability of the server to store information, the database remains the primary warehouse for data. The database is used to store data as a back end in stateful architecture while the server stores the information exchanged during a session of multiple transactions. 

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Takeaway

The difference between stateful and stateless does not just apply to networking protocols or cloud systems. Any application, architecture, server, or IT infrastructure resource that tracks information regarding its state, is known as a stateful resource. They are more reliable but may not be ideal for real-time performance, which must work without downtime. In that case, stateless would be the way to go. Organizations must know the differences between stateful and stateless to optimize performance while driving reliability and scalability. 

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