The integration pattern you choose early shapes everything downstream — how failures are handled, how the system scales, and how much a future developer has to relearn just to make a small change. This isn’t a preference decision between three roughly equivalent options. It’s an architecture decision with real tradeoffs, and getting it wrong is expensive to unwind once a dozen processes depend on it.
REST APIs
When to use: most modern, high-volume, real-time use cases — the default starting point for a new integration in 2026.
Pros: lightweight, widely supported across virtually every modern system, and well suited to mobile and web clients that need fast, predictable round-trips.
Cons: less built-in enterprise tooling than a middleware platform — monitoring, retry logic, and orchestration across multiple systems are things you build yourself rather than get out of the box.
Example scenario: syncing order status from an e-commerce platform into Salesforce in near real time, so support agents see current fulfillment status without switching systems.
SOAP
When to use: legacy system compatibility, or when the system on the other end has strict contract requirements that predate REST’s dominance.
Pros: strong typing and a formal contract (WSDL) that some older enterprise systems — particularly in finance and healthcare — still expect.
Cons: verbose payloads, heavier overhead per call, and tooling that feels dated next to a modern REST or event-driven stack.
When it’s legacy-only: in practice, SOAP is rarely the first choice for a new integration in 2026 — it shows up when the system on the other end doesn’t support REST and migrating that system isn’t in scope.
Middleware (MuleSoft)
When to use: multiple systems, complex orchestration, or integration patterns you expect to reuse across the org rather than build once and forget.
Pros: centralized monitoring, reusable APIs, and a single team that can own integration patterns instead of every point-to-point build being bespoke and undocumented.
Cons: licensing cost and added infrastructure — middleware is a real commitment, not a lightweight add-on, and it needs a team with the bandwidth to own it.
Enterprise benefit: when an org has five or more systems that all need to talk to each other, middleware turns a combinatorial mess of point-to-point integrations into a hub every new system connects to once.
Comparison table
| Pattern | Best use case | Scalability | Cost | Maintenance |
|---|---|---|---|---|
| REST | Real-time, high-volume, modern systems | High | Low | Owned per-integration |
| SOAP | Legacy systems with strict contracts | Moderate | Low–Moderate | Owned per-integration |
| Middleware | Multiple systems, complex orchestration | Very high | Higher (licensing) | Centralized |
Decision framework
- Number of systems involved: two systems rarely justify middleware. Five or more usually do.
- Real-time vs. batch need: real-time favors REST or Platform Events; batch tolerates SOAP or scheduled jobs either way.
- Existing infrastructure: if middleware is already licensed and staffed, use it — don’t build a parallel pattern outside it.
- In-house maintenance capacity: middleware without a team to own it becomes a liability faster than a well-documented point-to-point REST integration.
Best practices, regardless of pattern
Design for failure — assume every call will eventually time out or return a bad payload, and decide up front what happens next. Monitor everything, so a failed sync surfaces as an alert instead of a customer complaint three weeks later. And document the contract — field mappings, expected error codes, retry behavior — so the next person maintaining the integration isn’t reverse-engineering it from production logs.