Composable commerce Load Testing and the peak performance challenge

More retailers are moving towards headless and, increasingly, composable commerce architectures, and we’re seeing that shift first-hand as customers replatform to composable.

Headless separates the customer-facing experience from the commerce backend. Composable takes that further, allowing retailers to build the wider commerce stack from independent services and components.

This is no longer a niche approach: MACH Alliance’s 2026 Enterprise Technology Report found that 92% of organisations surveyed had implemented or were actively adopting composable technology. 

As AI and agentic commerce accelerate, the flexibility of these modular architectures is becoming even more valuable. Gartner’s 2026 Hype Cycle for Digital Commerce highlights the transformative potential of composable and modular architectures, particularly as a foundation for agentic applications. 

It’s easy to see the attraction. Retailers gain greater flexibility to introduce new technology, choose best-of-breed solutions for individual components and create new customer experiences without replacing an entire platform.

That flexibility creates huge opportunity. But ahead of BFCM and Christmas, it also changes the performance challenge and what retailers need to test to be confident at peak.

More moving parts to manage

Traditional eCommerce platforms also rely on APIs and third-party services. The difference with composable is that more of the core experience is modular, with independent components that can be developed, deployed and scaled separately.

That flexibility is one of composable commerce’s biggest advantages. But performance also depends on those components, and the connections between them, working effectively together.

Under peak load, a bottleneck doesn’t necessarily sit within the main commerce platform. It could emerge in an API, a separately scaled service or the interaction between components, and then affect the end-to-end customer journey.

AI can add another layer, as retailers introduce new services and integrations into an already distributed architecture.

Each component may perform perfectly well independently. The real test is what happens when they all have to work together under peak load.

There’s good reason to take that risk seriously.

Scale doesn't automatically mean peak-ready

This isn't an argument against composable commerce. Its flexibility and ability to support rapid innovation are exactly why so many businesses are adopting it.

But through Load Testing our customers' replatformed sites, we've also seen issues emerge between components, APIs and infrastructure that aren't apparent under normal traffic levels.

In one composable replatform, Load Testing uncovered an autoscaling configuration issue that triggered spikes in errors every time the platform scaled. Once traffic reached around 3,000 concurrent users, those errors escalated, causing issues including 500 errors, empty product listing pages and failed filters, all problems that could have directly impacted conversion at peak.

A platform may be cloud-based, individual services may be scalable and autoscaling may be configured. None of those things alone proves that the business critical customer journeys will work when the whole ecosystem comes under pressure.

That's why testing a composable platform ahead of peak needs to look beyond individual components and infrastructure metrics. It needs to recreate real customer journeys across the complete ecosystem, testing from the outside in to understand how everything behaves together as demand increases.

Being composable, scalable and AI-ready doesn't automatically mean being peak-ready.

Is your composable platform ready for peak?

Explore our fully managed customer journey-based Load Testing Service  and help protect revenue and customer experience throughout BFCM and the festive season.