Serverless computing and containers are architectures that reduce overhead for cloud-hosted web applications, but they differ in several important ways. Containers are more lightweight than virtual machines, but serverless deployments are even more lightweight and scale faster than container-based architectures.
Serverless computing vs. containers
Both serverless computing and containers enable developers to build applications with far less overhead and more flexibility than applications hosted on traditional servers or virtual machines. Which style of architecture a developer should use depends on the application’s needs, but serverless applications are more scalable and usually more cost-effective.
What are containers?
A container ‘contains’ an application and all the elements the application needs to run correctly, including system libraries, system settings, and other dependencies. Like a ‘add water pancake mix, containers only need one thing – to be hosted and run – to perform their function.
Any application can be run in a container. A containerized application will run the same way wherever it is hosted. Containers can easily be moved around and deployed wherever needed, much like physical shipping containers, which are a standard size and can therefore be shipped anywhere via a variety of means of transport (ships, trucks, trains, etc.) regardless of their contents.
In technical terms, containers partition a machine or server into separate user space environments. Each environment runs only one application and doesn’t interact with any other partitioned sections on the device. Each container shares the machine’s kernel with other containers (the kernel is the operating system’s foundation, and it interacts with the computer’s hardware). Still, it runs as if it were the only system on the machine.
Containers vs. virtual machines
A virtual machine is software that imitates a complete computer system. It is isolated from the rest of the machine that hosts it and behaves as if it were its only operating system, including its kernel. Virtual machines are another common way of hosting multiple environments on one server, but they use more processing power than containers.
What is serverless computing?
Serverless applications are broken up into functions and hosted by a third-party vendor who charges the application developer only based on the amount of time each process runs. For more on serverless computing, see What is serverless computing?
What are the critical differences between serverless computing and containers?
Physical machines
‘Serverless’ computing runs on servers, but it is up to the serverless vendor to provision server space as the application needs; no specific machines are assigned for a given function or application. On the other hand, each container lives on one device at a time and uses that machine’s operating system, though they can be moved easily to a different machine if desired.
Scalability
In a container-based architecture, the developer determines the number of containers deployed in advance. In contrast, in a serverless architecture, the backend inherently and automatically scales to meet demand.
To continue the shipping container metaphor, a shipping company could try to forecast an increase in demand for a specific product and ship more containers to the destination to meet that demand. Still, it could not snap its fingers and produce more containers full of goods if the request were to exceed expectations.
Serverless architecture is a way to do precisely that. Regarding computing power, serverless computing is like a water supply in a modern home: by turning on the tap, consumers can acquire and use as much water as they need and only pay for what they use. This is far more scalable than buying water one bucket or shipping container at a time.
Cost
Containers are constantly running; cloud providers must charge for the server space even if no one uses the application.
A serverless architecture has no continued expenses because the application code does not run unless it is called. Instead, developers are only charged for the server capacity that their application does, in fact, use.
Maintenance
Containers are hosted in the cloud, but cloud providers do not update or maintain them. Developers have to manage and update each container they deploy.
From a developer’s perspective, a serverless architecture has no backend to manage. The vendor handles all management and software updates for the servers that run the code.
Time of deployment
Containers take longer to set up initially than serverless functions because it is necessary to configure system settings, libraries, etc. Once configured, containers take only a few seconds to deploy. However because serverless functions are smaller than container microservices and do not come bundled with system dependencies, they only take milliseconds to deploy. Serverless applications can be live as soon as the code is uploaded.
Testing
It is challenging to test serverless web applications because the backend environment is hard to replicate in a local environment. In contrast, containers run the same no matter where they are deployed, making it relatively simple to test a container-based application before deploying it to production.
How are serverless computing and containers similar?
Both are cloud-based and significantly reduce infrastructure overhead – serverless computing more than containers. In both architectures, applications are broken down and deployed as smaller components. In a container-based architecture, each container will run one microservice.
What are microservices?
Microservices are segments of an application. Each microservice performs one service, and multiple integrated microservices combine to make up the application. Although the name seems to imply that microservices are tiny, they do not have to be.
One of the advantages of building an application as a collection of microservices is that developers can update one microservice at a time instead of updating the entire application when they need to make changes. Building an application as a collection of functions, as in a serverless architecture, offers the same benefit but at a more granular level.
How should developers choose between serverless architecture and containers?
Developers who choose a serverless architecture can release and iterate new applications quickly without worrying about whether the application can scale. In addition, if an application does not see consistent traffic or usage, serverless computing will be more cost-efficient than containers because the code does not need to be constantly running.
Containers give developers more control over the application’s environment (although this also comes with more maintenance) and the languages and libraries used. Because of this, containers are handy for migrating legacy applications to the cloud since it is possible to replicate the application’s original running environment closely.
And finally, it is possible to use a hybrid architecture, with some serverless functions and some functions deployed in containers. For instance, if an application function requires more memory than allotted by the serverless vendor, if a process is too large, or if certain parts but not others need to be long-running, a hybrid architecture enables developers to reap the benefits of serverless while still using containers for the functions serverless cannot support.
