APIs change. Integrations break. Documentation helps, but it does not always tell you what will happen inside your environment.
Marketing operations teams have spent years connecting platforms, CRMs, reporting systems, data warehouses, middleware, and custom applications. Once those connections work, it is easy to think of them as permanent infrastructure.
They are not.
Platforms retire APIs. Authentication standards change. Endpoints disappear. Version support ends. Fields behave differently. A migration that looks straightforward on paper can expose years of dependencies that nobody remembers until something stops moving.
That is exactly why API deprecation belongs on the marketing operations roadmap, not just the IT backlog.
Marketo SOAP is no longer a future problem
Adobe Marketo Engage ended support for its SOAP API on July 31, 2026 and directs integrations to the Marketo REST API. Adobe also deprecated use of the REST API access_token query parameter after August 31, 2026, requiring authentication through the Authorization header instead.
Adobe's guidance is clear: migrate SOAP-based integrations to REST. The operational reality can be less clean. A connection may depend on authentication, custom middleware, field mappings, CRM synchronization, activity retrieval, data warehouse exports, or downstream processes that were built years ago.
Read Adobe Marketo Engage's SOAP-to-REST migration guidance.
Salesforce is changing the API floor too
Salesforce follows an API end-of-life policy that retires older SOAP, REST, and Bulk API versions over time. Versions 21.0 through 30.0 are already retired and unavailable, while versions 31.0 through 40.0 are scheduled to become unsupported in Summer 2027 and retired in Summer 2028. Salesforce has also announced that the SOAP API login() call is scheduled for retirement in Summer 2027.
That matters because a Marketo-to-Salesforce environment is not one connection. It is two platforms, multiple APIs, authentication methods, sync rules, custom objects, integration users, and often additional middleware or custom logic sitting between them.
Review Salesforce's SOAP API end-of-life policy.
This is not unique to Adobe or Salesforce
Oracle Eloqua removed its legacy EloquaService SOAP API with its 22D release. Klaviyo uses a formal API lifecycle in which revisions move from stable to deprecated to retired, with developers generally given two years from release before a revision is retired.
The platforms differ, but the operating lesson is the same: integrations have a lifecycle. They need owners, documentation, monitoring, testing, and a plan for change.
See Oracle Eloqua's developer changelog and platform notices.
Review Klaviyo's API versioning and deprecation policy.
Why “follow the documentation” is not always enough
Documentation tells you what the platform expects. It does not know what your organization built around it.
A technically correct API migration can still create operational problems if a downstream process depends on an old response format, if an integration user lacks a permission, if authentication changed, if a custom mapping was never documented, or if the new connection works but no longer supports the same business process.
That is why testing only for a successful connection is not enough.
The right question is: does the complete business process still work?
Map the dependency before you make the change
Before replacing an API, connector, or authentication method, document what depends on it. At minimum, identify:
- the source and destination systems;
- the integration owner and business owner;
- authentication and integration users;
- objects, fields, activities, and data being moved;
- middleware, custom code, webhooks, or scheduled jobs;
- campaigns, lead routing, scoring, lifecycle processes, and automations that depend on the data;
- reporting, attribution, and downstream analytics using the connection; and
- the test cases required to prove the entire workflow still works.
This is less glamorous than a new AI feature. It is also the work that keeps marketing running.
API management is now part of marketing operations
Modern MOPs teams cannot treat integrations as “set it and forget it.” The stack changes too quickly, and the cost of a broken connection reaches far beyond the API itself.
A failed or incomplete migration can affect lead routing, campaign execution, lifecycle processing, CRM synchronization, attribution, reporting, personalization, and the data AI depends on to make decisions.
The cleaner your operating model is before the change, the easier it is to troubleshoot when the documentation and the real world do not line up perfectly.
Leadous helps teams design, troubleshoot, and strengthen the integration layer across marketing platforms, CRMs, APIs, middleware, and custom systems so the business process holds up when the technology underneath it changes.
Explore Leadous Integrations & System Connectivity.
Frequently asked questions
Is the Marketo SOAP API still available?
No. Adobe states that the Marketo Engage SOAP API was deprecated and became unavailable on July 31, 2026. Existing SOAP integrations should be migrated to the Marketo REST API.
Is Salesforce retiring SOAP API entirely?
No. Salesforce continues to support current SOAP API versions, but older versions are deprecated and retired on a lifecycle. Salesforce has also announced a future retirement of the SOAP API login() call.
What should teams test after an API migration?
Test more than authentication or a successful API response. Validate the full business workflow, including data movement, field mappings, lead routing, campaign automation, CRM synchronization, reporting, attribution, error handling, and downstream systems.
Who should own API deprecation planning?
Ownership may be shared across IT, engineering, platform administrators, and marketing operations, but MOPs should have visibility into any API or integration that affects campaign execution, customer data, lifecycle processes, reporting, or revenue operations.