The “Apex heap size is too large” error typically occurs when the bundle structure in Salesforce CPQ becomes overloaded. In practical terms, each time you nest bundles within bundles more than two levels deep—imagine a parent bundle, product options, and then even more nested product options—the system is tasked with loading all of that data simultaneously. This strain can quickly surpass the allowed heap size:

• The standard heap size limit is 8.7 MB for a bundle without special configuration.
• If your bundle’s structure exceeds this limit, you’ll see the error appear.

Solution: Enable Large Configuration

If your bundle size is just over the threshold, you can alleviate the issue by enabling Large Configuration on the product record:

• Locate the checkbox for Large Configuration on the relevant product.
• Enabling this converts the transaction from synchronous to asynchronous, raising the heap size limit to 12 MB.

However, this is a workaround, not a long-term solution. As you continue to add nested bundles, even this higher limit can be exceeded. Additionally, enabling this setting may slow down the quote creation process, as loading large bundles asynchronously is a more resource-intensive operation for Salesforce.

Best Practice:

• Limit your bundle nesting to no more than two levels deep to avoid recurring errors and performance issues.