Hot take incoming. I’ve built a custom order management system (OMS) and worked on a SaaS OMS implementation for a major retailer. And for some of the most complex retail operations, I’d still bet on a custom build.
I know that’s a strong take. But if the fulfillment rules your business depends on are the ones a platform struggles to support, you’re going to pay for that gap somewhere. Let me tell you what I actually saw.
What Building a Custom OMS Gave Us
The company I worked with early in my career built their OMS from the ground up. And honestly? It was impressive.
Not because it was technically elegant (it wasn't always). But because it was theirs. Every business rule, every edge case, every weird fulfillment scenario that would make a SaaS vendor shrug and say "that's a configuration limitation" was handled. The system bent around the business, not the other way around.
The smartest decision they made was designing the business logic to be modular and domain driven. Rules weren't hardcoded into the execution layer. They were externalized, configurable, and in many cases lift-and-shiftable. When the business changed (and in retail, the business always changes) you didn't have to gut the system. You updated a rule. You swapped a module. You extended a pattern that already existed.
One thing people underestimate about custom builds is the phasing flexibility. You can build one capability, phase out that piece of the legacy system, and take your time building the next. The business keeps running. You are not doing a big bang cutover where everything changes at once. What I liked about that build was how much control we had over the sequence. We could retire one legacy capability and decide when we were ready to tackle the next.
But I want to be honest about the other side of it too. Custom builds are expensive. Not just to build, but to sustain. You need a dedicated engineering team, ongoing infrastructure investment, and the budget to keep evolving it as the business grows. This is not a one-time cost, it is a continuous commitment. And the timeline is long. We are talking months, sometimes years, before you see the full system running. If your organization is not prepared for that, the custom path will hurt you eventually even if the initial build goes well.
When you get it right, a custom OMS is genuinely unbeatable for complex operations. And when you get it wrong, when the logic is buried, when the original architects have left, when every change requires archaeology, it becomes a liability that no amount of SaaS migration excitement can fully fix.
What Surprised Me About Implementing a SaaS OMS
I am in the middle of a SaaS OMS implementation right now, so I will be careful here. But I will be honest.
The speed-to-value argument is real. You are not building infrastructure. You are not managing servers. The vendor handles upgrades, and the ecosystem of connectors is genuinely better than anything a custom build gives you out of the box. For a mid-market retailer with a reasonably standard operating model, SaaS is probably the right answer today and I would not argue against it.
But here is the thing: SaaS OMS platforms have opinions. Strong ones. And you will feel them.
When your business has a legitimate operational need that does not fit neatly into those opinions (which it will, because complex retail is complex) you have a few options. You configure around it. You file an enhancement request and wait. Or you build a middleware layer that does what the platform won't. None of those options are free. And the implementation timeline always reflects it.
The other thing people underestimate is parallel maintenance. When the legacy system and the new OMS both need to support the same order flows during a transition, you’re maintaining and testing those flows in two places. Before you settle on a rollout plan, ask which flows you can move independently and how long you’ll have to support both.
The "faster to value" story is true for the first 70% of scope. The last 30%, the edge cases, the integration quirks, the business rules that don't have a config checkbox, that is where the complexity lands. And that complexity doesn't disappear just because you bought a SaaS product. It just moves into your middleware and integration layer, which your team now owns and maintains.
When Should Retailers Build, Buy, or Do Both?
Custom build is right for you if your operational complexity is genuinely differentiated, you have a team that can architect modular business logic, the budget to sustain it long term, and the patience for a multi-year horizon. Do it because your business model genuinely won't fit in a box.
SaaS OMS is the right default for most retailers today. Faster to get running, lower operational burden, better out-of-the-box ecosystem. But go in with eyes open. The platform has opinions, the implementation is harder than the demo suggests, and the parallel maintenance burden is real.
Do both when the platform handles most of your order flows and a few decisions are worth owning. Say your sourcing rules weigh store capacity, delivery promises, and inventory you need to protect for walk-in shoppers. You could use the platform for the core order lifecycle and own that sourcing logic separately. The question I’d ask is who will test and support that handoff when an order goes sideways.
Here is a side-by-side of what the decision actually looks like in practice:
| Custom Build | SaaS OMS | |
| Implementation timeline | Slow. Months to years depending on scope and complexity. | Fast. Significantly faster path to go-live. |
| Phasing flexibility | Roll out one capability at a time where the architecture lets you separate it from the legacy OMS. | Phase the rollout where the platform and integrations allow order flows to move independently. |
| Parallel maintenance | Legacy overlap depends on when each capability and its dependencies can be retired. | Plan to maintain and test any order flows that both systems must support during cutover. |
| Flexibility to change | Full liberty. You own the logic, change it anytime for any reason. | Constrained. Bound by platform opinions, release cycles, and enhancement request queues. |
| Ongoing cost | High. Dedicated team, infrastructure, and continuous investment, not a one-time cost. | Lower. Vendor manages infrastructure and upgrades, operational burden shifts off your team. |
| Business fit | System bends around your business model. | You adapt your processes to fit the platform's model. |
| Edge case handling | Build exactly what you need, tuned to your operation. | Configure around it, wait for an enhancement, or build middleware. |
One More Thing About AI in Order Management
This deserves its own mention because it is changing the conversation fast.
SaaS OMS platforms are now shipping AI agents as part of their offering. And honestly, some of it is genuinely useful. Think about your customer service team and how much of their day is spent answering the same questions. Where is my order? Can you cancel this? I forgot to apply a coupon during checkout. These are repetitive, manual tasks that eat up CSR time every single day. SaaS platforms are now offering agents that handle exactly this: answering order status queries, processing cancellations, applying coupons, all without a human having to touch it. That is real value and it is available to you quickly when you are on a SaaS platform.
But here is what I keep thinking about. Those agents are scoped around what the vendor decided your operation needs. With a custom build, you are not limited to that. You can build an agent for any part of your workflow, not just customer service, but warehouse operations, inventory reconciliation, fulfillment exception handling, whatever your business actually needs. You define the scope, the behavior, and the logic. Not the vendor's template. Yours.
SaaS gives you AI faster. Custom gives you AI that fits better. That trade-off is real and it is only going to matter more as AI becomes a bigger part of how OMS platforms compete.
The honest truth is this: the build vs buy debate has a new answer every few years because the technology and the economics keep shifting. What has not changed is that the wrong answer is always the one made without fully understanding your own operational complexity first.
Deciding what to build, buy, or keep in your OMS?
Nextuple can help you compare those options against your hardest order and fulfillment scenarios, the cost of owning each solution, and what your team can realistically support after go-live.
Adapted from an article originally published on LinkedIn on May 25, 2026
