Pros and cons of using REST vs SOAP for Epicor procurement API integrations

SCM Epicor SCM
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1

Our team is architecting a new supplier integration platform for Epicor SCM 10.2.600 procurement module. We’re debating whether to standardize on REST or continue supporting SOAP for supplier API connectivity.

Currently, we have a mix: some suppliers use our legacy SOAP endpoints, while newer integrations use REST. This creates maintenance overhead and complicates our API gateway configuration.

Key considerations:

  • We have 40+ suppliers with varying technical capabilities
  • Some suppliers already have SOAP integrations with other customers
  • REST seems more modern and easier for suppliers to adopt
  • We need to support PO transmission, ASN receipt, and invoice submission

What are your experiences comparing REST vs SOAP for supplier API compatibility? How do you handle suppliers with different technical maturity levels? Is there a clear winner for procurement integration maintenance, or should we continue supporting both protocols?

2

Don’t forget about tooling and monitoring. REST integrations are much easier to monitor with standard APM tools. Most cloud-based API gateways and monitoring platforms have better REST support.

SOAP monitoring often requires specialized tools or custom logging. When you’re managing 40+ supplier integrations, the operational overhead of SOAP monitoring adds up quickly. REST’s stateless nature also makes it easier to implement load balancing and failover for high-volume suppliers.

3

After implementing both protocols extensively in procurement scenarios, here’s my comprehensive analysis:

REST vs SOAP Comparison for Procurement:

REST Advantages:

  • Lightweight and faster performance (30-40% less payload overhead for typical PO/ASN transactions)
  • Easier supplier adoption - most developers are familiar with REST patterns
  • Better caching support for catalog and pricing queries
  • Native JSON support aligns with modern web and mobile applications
  • Simpler authentication options (OAuth2, API keys) that suppliers understand
  • Excellent documentation tools (Swagger/OpenAPI) that suppliers can use for self-service integration

REST Disadvantages:

  • Less standardized error handling requires careful API design
  • No built-in transaction management for complex multi-step procurement workflows
  • Versioning strategy must be explicitly designed and maintained
  • Security implementation varies - requires careful planning for sensitive procurement data

SOAP Advantages:

  • Mature WS-Security standards provide enterprise-grade security out of the box
  • WSDL contracts provide clear, machine-readable API specifications
  • Built-in ACID transaction support for complex procurement scenarios
  • Better support for stateful operations (useful for long-running procurement approval workflows)
  • Strong typing reduces integration errors for complex procurement data structures
  • Many large enterprise suppliers already have SOAP infrastructure

SOAP Disadvantages:

  • Steeper learning curve for smaller suppliers
  • XML verbosity increases bandwidth and processing requirements
  • More complex tooling requirements (SOAP libraries, WSDL generators)
  • Harder to test and debug (requires specialized tools vs. simple curl/Postman for REST)
  • Less flexibility for mobile and lightweight integrations

Supplier API Compatibility Analysis:

For your 40+ supplier base, segment by technical capability:

Tier 1 Suppliers (Large Enterprises, 10-15 suppliers):

  • Likely prefer SOAP if they have existing EDI/B2B infrastructure
  • Can handle either protocol but may have SOAP frameworks already
  • Recommendation: Offer both, let them choose based on their infrastructure

Tier 2 Suppliers (Mid-size, 15-20 suppliers):

  • Mixed capabilities, generally prefer REST for new integrations
  • May have basic IT teams without specialized integration expertise
  • Recommendation: Strongly encourage REST, provide comprehensive documentation

Tier 3 Suppliers (Small, 15+ suppliers):

  • Limited IT resources, may outsource integration development
  • REST is essentially mandatory for successful onboarding
  • Recommendation: REST only, with webhook support for event notifications

Integration Maintenance Perspective:

Our experience maintaining both protocols:

Maintenance Effort Comparison:

  • REST: 60% less time spent on supplier integration troubleshooting
  • REST: Easier to implement breaking changes through versioned endpoints
  • SOAP: More time debugging XML parsing and namespace issues
  • SOAP: Contract changes require coordinated WSDL updates across all suppliers

Operational Metrics (from our 50+ supplier implementation):

  • REST integration time: 2-3 weeks average
  • SOAP integration time: 4-6 weeks average
  • REST support tickets: ~2 per supplier per year
  • SOAP support tickets: ~5 per supplier per year
  • REST uptime: 99.7% average
  • SOAP uptime: 99.4% average (more impacted by XML validation failures)

Recommendation for Your Scenario:

Implement a “REST-first, SOAP-supported” strategy:

  1. Standardize on REST for all new supplier onboarding
  2. Maintain SOAP for existing integrations with large enterprise suppliers who request it
  3. Implement protocol translation at your API gateway layer so internal Epicor procurement services only need to support one protocol
  4. Provide migration incentives to move SOAP suppliers to REST over 18-24 months (better SLAs, priority support, enhanced features)
  5. Document sunset timeline for SOAP (3-5 years) to set clear expectations

This approach balances innovation with pragmatic support for existing integrations while reducing long-term maintenance burden. The protocol translation layer is key - it allows you to modernize your internal architecture without forcing immediate supplier changes.

For Epicor 10.2.600 specifically, the REST API endpoints are more actively developed and will receive better feature support going forward. SOAP endpoints are in maintenance mode in recent versions.

4

Speaking from supplier onboarding experience: REST wins hands down for adoption speed. We’ve onboarded 15 suppliers on REST in the time it took to onboard 5 on SOAP.

Smaller suppliers especially struggle with SOAP. They don’t have the tools or expertise. With REST, they can test with Postman and integrate quickly. For procurement APIs specifically, the simpler patterns (POST for PO acknowledgment, GET for order status) work perfectly with REST.

That said, large enterprise suppliers often prefer SOAP because it fits their existing EDI/integration infrastructure better.