It’s time to replace the aging systems in your warehouses and everyone in the organization knows it. Your WMS has reached its end-of-life for support. (Not to mention its incompatibility with the rest of your tech stack and some security concerns.) And your WCS is reaching the limits of its ability to support new automation initiatives.
Being the technology leader in your organization, you are trying steer your company down the right path for modernizing and future-proofing your system investments. But which way should you turn? What’s the right road to take?
You could invest in an all-out new, latest, greatest best of breed WMS like last time—one that has all the bells and whistles that have been added and developed since version “X” years ago. But what about the WES thing everyone is talking about? Could it pick up the slack or bridge the gaps with your existing WMS? Would a leaner Tier 2 WMS suffice, especially if you’re going to be replacing the control layer as part of this journey? And what about the claims that WES can “do it all” – even integrate to your Order Management Systems or ERP in lieu of your WMS? Do you even need a WMS anymore?
In this post, I'll walk you through a practical, honest evaluation of how to assess your WMS needs, especially if a WCS-to-WES upgrade may be part of your roadmap.
The Warehouse Technology Arena: WMS vs. WES vs. WCS
Before we get too far, let’s make sure we understand all the acronyms. First up and probably the most well known is the Warehouse Management System or WMS. But what does a WMS level or tier imply? While there isn’t a true technical definition, most of us in the industry would categorize WMS tiers as follows:
- Tier 1 WMS: These platforms are full-featured systems, built for large, complex operations that need heavy configuration, international support, labor management, slotting, billing, and advanced workflows. In addition, they offer high levels of user configurability, functional extensibility, and standard integrations to multiple external systems like WCS, ERP, third-party shipping solutions and other APIs and edge apps.
- Tier 2 WMS: These platforms on the other-hand offer basic WMS functionality but are often faster to implement. While still possible to varying degrees, customizations and modifications are not as common or elaborate with Tier 2 platforms and out-of-the-box integrations are not as comprehensive. The main tradeoff is typically a lower total cost of ownership.
Then there’s the rise of Warehouse Execution Systems or WES. Although WES applications and technology can be traced back at least a couple of decades, it’s only been in recent years there has been a resurgence in this solution and how it is reshaping warehouse architecture.
In the past, a Warehouse Control System (WCS) acted as a “traffic cop” for automation, playing that supervisory role over single or aggregated automation solutions. Meanwhile the WMS played the role of big decision maker regarding what to do in the warehouse. A WES positions itself in between the WMS and the WCS, and in some cases directly on top of all the automation when it can fully replace the WCS, while adding dynamic task orchestration, equipment balancing, and real-time decision-making for automated environments.
Many distribution and fulfillment organizations are now pairing a robust WES with a right-sized WMS. But this is where it gets tricky.
WMS vs. WES: Who’s in charge of what?
There’s an adage that goes something like “Let good people do what they do best.” And the reality is, one can apply that same principle to your technology solutions. With that in mind, this is where clear delineation matters:
- WMS excels at inventory and location control, ERP integration, order management, and handling complex business rules. Historically this is what these systems were designed and engineered for, and they still excel at it.
- WES by contrast excel at orchestrating tasks across automation and robotics, managing real-time constraints and opportunities, and optimizing and allocating equipment usage. Like WMS, there have been years of research and development into those capabilities.
But as is the tendency, as you get great at one thing, you start to take on more, and that is why overlap is growing—and so is the corresponding confusion.
Many Tier 1 WMS solutions now include task prioritization, wave-less picking, and even some orchestration logic as part of their out-of-the-box features and capabilities. In the past these abilities were more often achieved through “bolt-on” applications or complex and costly extensions that didn’t port well to future versions of WMS and offered little flexibility to change with dynamic business environments. Concurrently, WES vendors who mostly based their earlier offers in WCS and automation supervisory software solutions are adding greater inventory visibility, dock scheduling, and order planning to the suite of features found in their packages. On paper, it’s not unusual for both of us to now claim to do everything.
But here’s an important point to remember regarding WES, as I’ve already noted, WES platforms are not ground-up unifications. They are, in many cases, legacy WCS systems enhanced with supervisory logic, and in some cases, they have grown from legacy WMS platforms rebranded with automation control features. This isn’t the first time the industry has promised a “single pane of glass” for warehouse operations. History reminds us to stay skeptical.
WES may be cheaper, but it doesn’t replace everything
It cannot be denied that a major attraction of WES is flexibility. Modifying a WES is typically less costly than modifying a WMS and can present a lesser degree of risk to the business during the deployment and validation of those changes—even when you consider the rise of extensibility frameworks in modern Tier 1 WMS platforms.
Want to reprioritize pick tasks based on resource or equipment availability? Encountering system congestion? Need a temporary rule for a promotion or added cutoff time? WES can handle it faster and often without deep vendor engagement. Whether the change is permanent or just through a unforeseen outage event or peak capacity period, WES can react quickly and dynamically to changing flow requirements.
However, WES platforms are not ideal for ERP integration. ERPs still integrate more naturally—and more cleanly—with WMS platforms. When one considers all the data interchanges that have to occur between a WMS and ERP, placing that burden onto a WES while the WES is also trying to manage real-time operation and utilization of electro-mechanical equipment, the inherent risk of trying to “do it all” becomes quite clear – something is going to give. Also, when attempting to bridge directly from ERP to WES without a WMS, data flow gaps can result along with missed inventory checkpoints, and audit trail inconsistencies. The WES is focused more on data required to operate and execute and less on data to account.
In short, don’t throw the WMS out with the middleware.
Choosing the right WMS in the context of WES adoption
1. Operational complexity
If you have thousands of SKUs and you’re trying to manage them across an omnichannel business with retail, ecommerce, and wholesale flows—each requiring unique and variable handling rules, customs documentation, or regulatory requirements—a Tier 1 WMS may still be necessary. These capabilities are baked in and ready to go with limited set-up and configuration.
However, if plan on off-loading real-time prioritization, inventory movement decisions, and dock balancing to a capable WES, you may not need all the horsepower—or cost—of a Tier 1 WMS. A Tier 2 with some potential enhancements might get you under the wire for what you really need.
2. Automation and robotics footprint
Few warehouses of the future will be absent from these growing technology solutions. If yours is one of those facilities introducing AMRs, AS/RS, shuttle systems, and sorters, then a WES will be vital in coordinating those systems, freeing the WMS to become more of a transactional and inventory-focused system. In these cases, Tier 2 WMS platforms—especially those with open APIs—can be a better fit.
Figure 2. An easy-to-use decision tree to help you choose which WMS is right for your business.
3. Existing middleware or custom solutions
Many companies have either externally sources or developed their own bolt-ons or integrations to make up for what their legacy WMS couldn't do. And they find themselves dependent on an ever-diminishing knowledge base to support those capabilities, such as task queueing, priority zones, wave control, even equipment throttling. If a modern WES can replace those custom elements, a Tier 1 WMS may no longer be justified, particularly if that new WMS will still need some degree of customization and extension for those features.
4. Long-term IT strategy
Is your company migrating toward more microservices, API-first architectures, or composable platforms? Tier 1 WMS platforms, in light of their inherent extensibility options, can often plug in easily and may still be required, regardless of the capability of a new WES.
Three real-world scenarios to bring it all together
Scenario 1: Ecommerce fulfillment center with robotics
You’re building a new DC with goods-to-person robotics, AMRs, and dynamic order streaming. A best-of-breed WES takes the orchestration lead. The WMS focuses on inventory integrity and ERP communication. A Tier 2 WMS suffices—and costs significantly less.
Scenario 2: Legacy DC replacing a patchwork of warehouse technology tools
You’re upgrading a 20-year-old WMS and replacing homegrown middleware for waving, priority logic, and slotting. In this case, a Tier 1 WMS can consolidate disparate tools and bring you to a stable baseline—unless your new WES can handle those functions more efficiently.
Scenario 3: High-regulation pharma or food distribution
Audit trails, compliance rules, serialized inventory, and integrations with MES or TMS systems are non-negotiable. Here, you likely need a Tier 1 WMS—even with a WES—because it’s still your system of record.
Which scenario is yours? Or do you have your own unique set of plans on your company’s roadmap that will requirement additional assessment and evaluation? Let's talk if you'd like some help to make the next best warehouse technology move for your business.
