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SaaS vs Open Source for Headless Commerce

An ever-growing number of consumers are choosing to engage with commerce online, and the trend shows no sign of slowing down.

Due to the growth of the ecommerce market, it's crucially important to select the right technology for ecommerce operations, because the choice of tech has the potential to impact significantly on the smoothness of operations and a retailer's bottom line.

With the incorrect tech stack, businesses risk loss of revenue, technical debt, and growth difficulty.

In contrast, a winning ecommerce architecture has the potential to smooth-over preexisting challenges by improving efficiency on the backend, whilst simultaneously meeting consumer demand through effective omnichannel experiences.

In this resource, we'll explore the core application architecture for Headless Commerce builds and make comparisons between an Open Source and SaaS (Software-as-a-Service) approach. These are the two most common choices of application implementation for Headless Commerce builds today, and form a major part of the decision making process in the run-up to a relaunch of a headless build for growing ecommerce stores.

As a Headless Commerce agency ourselves, these views encapsulate our experience, including feedback we've received from clients, having worked with numerous online retailers to build and service complex ecommerce builds that utilize a headless or composable approach.

First what is Headless Commerce?

Headless Commerce is the gold-standard for ecommerce architecture implementation today. This approach works differently than a traditional ecommerce setup, primarily by the decoupling of the ecommerce backend from the frontend experience or storefront.

Headless Commerce involves a separation of the presentation layer (frontend storefront) from the backend (an ecommerce management system), allowing for multiple frontend experiences or distribution through various commerce channels (omnichannel commerce), with connections to the backend or data sourcing occurring through APIs.

Headless Commerce aims to address various challenges associated with the reliance on a single application or piece of software for delivery and operations of the entire commerce build, allowing for appropriate selection of technology and an increased ability to service multiple commerce channels from a single backend.

For growing online retailers, Headless Commerce is positioned to address a variety of challenges particularly associated with user experience design + optimization, growth, and efficiency of operations.

A Headless Commerce setup will require a central ecommerce management system, in much the same way as a traditional ecommerce setup, where products, collections, and orders are managed and serviced.

In this article, we'll address the potential options available for this core part of the stack architecture, including the differences between open source and SaaS ecommerce management systems, how they differ, and where they are best placed.

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What is an Open Source E-commerce Management System?

Open Source ecommerce management systems are the most commonly implemented for the development of ecommerce stores in general, across the web.

"Open source" ecommerce platforms allow for the application's code to be openly inspected, edited, and customized. Some examples of Open Source ecommerce management systems include:

  • WooCommerce
  • Magento Open Source (Adobe Commerce Open Source)
  • Prestashop
  • Drupal Commerce
  • OpenCart

With Open Source ecommerce, the system can be freely modified or extended to support custom implementations aimed at specific business needs.

The majority of e-commerce stores follow a traditional and predictable format, in the sense that products may list a simple set of variants and attributes (think T-Shirts in different sizes and colors), and shoppers can add these to their cart directly.

But for some ecommerce stores, requirements can be highly-custom — demanding specific workflows in order to achieve both frontend and backend business requirements and logic.

For instance, many businesses offer products which are highly configurable: formed of a large number of interchangeable components which can be altered by the user to achieve a bespoke or made-to-order build.

In some instances, made-to-order products will utilize a predictable number of variants and attributes (eg. a sofa in a variety of colors). But more complex products, such as a bespoke heating system, a vehicle, or a musical instrument, can potentially include a vast number of configurable components which form the end product.

For brands who sell products which are highly customizable, an out-the-box solution is unlikely to cater to the specific requirements of their product line.

The same can apply to non-traditional commerce setups, such as vendor/distributor marketplaces, retailers who sell services, or B2B ecommerce. All of these verticals have a high likelihood of requiring custom business logic to apply to an ecommerce system, in order for it to be efficient and effective.

Open Source ecommerce platforms can present an attractive solution in some of these cases, due to the fact that their source code can be freely modified and enhanced to achieve the custom logic required for a successful implementation.

Open Source e-commerce management systems are free to download, use, and deploy, requiring no up-front cost in order to gain access to or implement the software itself. In other words, they don't require licensing fees or recurring subscription fees to access and deploy them.

What is a SaaS e-commerce system?

SaaS stands for "Software as a Service", and in the context of ecommerce, refers to a serviced/managed platform providing ecommerce tooling to businesses out-the-box. Businesses pay a monthly fee in order to access and utilize a SaaS ecommerce platform on an ongoing basis.

With SaaS ecommerce platforms, it's often the case that the provider does not permit access to the source code, or the rights to modify the source code itself.

With SaaS products, the route to customization or implementation of custom business logic is often achieved through development of bespoke plugins or extensions that are capable of altering the existing processes of the software, or, more often, adding further processes when certain actions occur (i.e. implementing a function containing logic for post-processing upon new order creation).

Some examples of SaaS e-commerce platforms are:

  • Shopify and Shopify Plus
  • BigCommerce
  • Adobe Commerce
  • Salesforce Commerce
  • Volusion
  • Wix
  • Squarespace

Most SaaS ecommerce platforms offer a straightforward route to development of an ecommerce store, whether new or via replatforming.

With SaaS ecommerce systems, the software is serviced and maintained by the platform operator itself, typically accessible via an administration portal through web browser.

Today, the most popular SaaS ecommerce platforms utilize a recurring subscription model, requiring businesses to commit to either monthly or annual billing for access to the platform.

Open Source vs SaaS for Headless Commerce: How do they compare?

There's a whole host of differences between Open Source and SaaS ecommerce platforms, but particularly in the context of Headless Commerce, the biggest difference lies in the way that custom business logic is performed, and the routes to achieving this.

For businesses who are utilizing Headless Commerce as a way to achieve a higher level of flexibility and custom business logic, defining the role of the core ecommerce management system is critical.

Subscription Fees

From a cost perspective, Open Source and SaaS ecommerce platforms differ greatly in terms of how and where funds are spent in the context of a headless build.

SaaS offerings provide an attractive, predictable pricing structure, but this will often be affected by the volume of traffic and engagement that the store sees, as well as the extent of any custom processing or batch operations that have been implemented to achieve specific data or functionality requirements.

Most SaaS offerings will enforce rate limiting on API requests and batch processing, requiring the enrollment into a higher level of subscription plan for growing ecommerce stores over time.

In contrast, open source ecommerce management systems come with no such restrictions, though a cost increase is likely to be felt elsewhere, such as the increasing server resources demanded due to a higher number of API requests to the open-source backend when higher levels of engagement is seen.

Open Source ecommerce systems don't require monthly subscription fees, but will require hosting infrastructure for the codebase and database, the cost of which will be determined by the resource consumption of the application; often closely tied to the traffic and performance requirements of the ecommerce store.


Potentially one of the biggest cost differences between open source and SaaS ecommerce solutions is the maintenance required of open source software.

Open Source ecommerce management systems will require frequent maintenance, additional to maintenance of the server environment to which they're deployed.

Many service providers or web hosts offer managed solutions, but this is an additional cost outlay when compared with maintained SaaS services. With SaaS solutions, maintenance requirements are offloaded to the operator of the platform, largely negating costs associated with maintenance of the backend application itself, on the whole.

In contrast, open source ecommerce solutions will require routine maintenance and upgrades of the application by a dedicated development team, in order to maintain optimal security and smooth operation of the application.

In addition to this, potential exists that the server environment hosting the application will require its own maintenance cycle, in order to ensure the security and integrity of the environment.

From this angle, SaaS offerings provide an attractive proposition in that they can largely reduce backend maintenance requirements for Headless Commerce builds. It's important to note, however, that the headless frontend(s) utilizing a SaaS backend will still require regular maintenance in a headless commerce build.

In our experience, headless storefronts will typically require a more involved maintenance program than traditional ecommerce builds, whether the backend is utilizing an Open Source or SaaS framework.


For the most part, headless SaaS ecommerce platforms will not require additional hosting costs beyond the recurring subscription fees. The ecommerce application is hosted by the SaaS provider, in which case maintenance and operation of the backend server architecture is completely negated for a headless build.

Open Source ecommerce systems will require hosting, whether cloud-based or dedicated, even when utilized within a headless architecture.

Typically, we find that the cost of hosting such a system for a medium-trafficked ecommerce store can be expected to exceed the cost of SaaS pricing in a side-by-side comparison, when taking into account other factors such as performance and resource consumption.

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Custom Development

Development methodology has the potential to vary significantly when comparing Open Source vs SaaS ecommerce solutions for Headless Commerce builds.

Largely, the difference will be felt to a greater or lesser degree depending on whether the headless build also utilizes a Composable approach, or is purely a headless backend servicing a decoupled JavaScript storefront.

A quick note on Composable architectures:

A composable approach to ecommerce differs from—but incorporates—headless commerce. With composable, an ecommerce tech stack will generally utilize a variety of different technologies, platforms, and providers, and involves heavy utilization of microservices.

In this case, it's likely that custom development or bespoke customization to the backend ecommerce management system will be reduced, when compared to a purely headless (non-composable) build.

This is because a composable build is less likely to rely on custom modification of the core ecommerce backend, and more so on the integration of various third-party tools and microservices in order to achieve the desired functionality.

For headless ecommerce storefronts which do not heavily modularize their tech stack, a larger amount of custom or bespoke development is likely to take place, in contrast to the high number of independent microservices and third-party integrations that a composable build might rely on.

A headless approach to ecommerce implementation allows for the development of custom business logic, functionality, or processes to occur outside of the SaaS platform's architecture itself.

It's commonplace for headless ecommerce builds to leverage multiple microservices in order to achieve the desired custom functionality or logic, with this living outside of the SaaS platform itself.

Alternatively, some SaaS products allow for custom plugins or extensions to be installed, which provides an additional route to bespoke functionality.

Performance perspective

With Open Source ecommerce systems, performance of the software stack will have to be monitored, optimized, and maintained in-house.

Specialist development teams with sufficient know-how will have the competence to implement appropriate performance optimization techniques where required, but will also ensure that code is written in accordance with best practice and in a performant fashion.

Where a codebase has been developed to a high standard, and appropriate technology has been selected for the particular project stack, excessive performance optimization is unlikely to be required; though reducing response times always provides benefit.

It's absolutely imperative that projects are scoped correctly and adequately prior to development, so that code can be written in the most efficient fashion from the outset, which helps avoid technical debt.

Retrospective performance optimization usually presents headaches: and has its limitations.

Where a headless ecommerce tech stack has been adequately scoped, carefully architected, and implemented using solid development techniques, performance should not be of concern.

It's expected that a degree of end-of-project optimization will be required to improve performance, such as the configuration of edge CDNs, caching of both backend processes and the frontend itself, asset optimization, etc., but these are straightforward implementations that shouldn't require too much in terms of resources.

In summary, because open source platforms are self-hosted, the responsibility for performance optimization falls on the development team or agency partner. However, this provides potentially limitless scope for performance improvements given the resources.

With SaaS-based offerings, developers are invariably limited to optimizing only parts of the stack within their own control, which usually means that SaaS ecommerce backends can only be optimized to a certain degree, if at all.

The mainstream ecommerce SaaS providers generally offer fairly good performance out-the-box, but we have experienced instances of backend latency when stores are housing a lot of data.

In these cases, the SaaS backend can become noticeably slower to respond, and there is a limited control to be had in order to address this with SaaS-based commerce solutions.

On the flip-side, open source solutions afford development teams an essentially limitless opportunity to improve backend performance, as the source code is open and freely accepts modification for optimization.

Will SaaS require additional custom technology implementations anyway?

Most headless builds running on SaaS backends will require some form of custom development in the form of microservices or plugins to extend the functionality in order to achieve custom business logic and functionality required of the build.

This is particularly true of ecommerce builds where the requirements are highly bespoke, involving features or functionality that is unique to the retailer, such as a custom product configurator, interactive look-books, etc.

Functionality perspective

In terms of available functionality, the backends of SaaS ecommerce platforms is generally fixed, with a limited ability to extend or override the functionality and processes of the system itself.

Arguably, this doesn't present a huge challenge in a headless or composable ecommerce build, as the functionality of the backend can be adjusted through custom development within other areas of the stack (i.e. a secondary post-processing backend application, or via the frontend when data is received from the backend).

Additionally, most SaaS ecommerce platforms will offer the ability for developers to build plugins or extensions that modify or extend the platform's backend behavior to some degree.

It's important to note that, while SaaS offerings won't allow as deep a level of customization as open source backends, they will generally provide sufficient control for most use cases. With headless or composable commerce, a far greater degree of flexibility can be achieved even when utilizing a SaaS ecommerce platform as a backend, when compared to a fully-hosted solution.

In conclusion, while backend functionality for SaaS-based ecommerce platforms is more rigid than with Open Source solutions, decoupled or composable builds can help to alleviate these challenges.

Future proofing

With Open Source e-commerce, you retain full control and ownership of the codebase, and can essentially do whatever you want with it.

This provides security as the code itself isn't going anywhere, and an open source ecommerce backend can theoretically survive indefinitely.

However, open source code needs to be maintained, updated, and secured, and will typically have a limited usable lifespan.

For open source ecommerce applications written in PHP for example, these will require updating periodically (in reality, fairly often), in order to maintain support for the latest version of PHP whilst retaining functionality.

This is the case regardless of which programming language the backend is written in. In this regard, open source solutions are high-maintenance in order to provide assured longevity, but this can be achieved through frequent updating and servicing of the software.

In contrast, SaaS ecommerce platforms don't require maintenance or updates as such. The responsibility for maintaining the integrity of the solution falls instead on the service provider, alleviating backend maintenance requirements for businesses.

It's not possible to determine the long-term future of any company, and the same is true for SaaS platforms providing paid ecommerce solutions.

Over the years to come, it's possible that some SaaS providers will adjust their offerings, be acquired, or perhaps eventually disappear completely.

However, the frontrunners in ecommerce-as-a-service don't appear to be going anywhere, and given how fast the tech industry moves it's arguably a folly to be overly concerned by this in relation to the major providers.

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