Composite operations (multi-resource) in Rest API - Step-by-Step Execution

Concept Flow - Composite operations (multi-resource)

Start Composite Operation

↓

Call API 1: Create Resource A

↓

Check API 1 Success?

No→Rollback if needed

Yes↓

Call API 2: Update Resource B

↓

Check API 2 Success?

No→Rollback API 1

Yes↓

Call API 3: Delete Resource C

↓

Check API 3 Success?

No→Rollback API 1 & 2

Yes↓

All Success

↓

End

The composite operation calls multiple APIs in order, checking success after each. If any fail, it rolls back previous changes to keep data consistent.

Execution Sample

Rest API

POST /resourceA
if success:
  PATCH /resourceB
  if success:
    DELETE /resourceC
    if success:
      return success
    else:
      rollback resourceA and resourceB
  else:
    rollback resourceA
else:
  return error

This code tries to create, update, then delete resources in sequence, rolling back if any step fails.

Execution Table

Step	API Called	Request	Response	Success?	Action Taken
1	POST /resourceA	Create Resource A	201 Created	Yes	Proceed to next API
2	PATCH /resourceB	Update Resource B	200 OK	Yes	Proceed to next API
3	DELETE /resourceC	Delete Resource C	500 Internal Server Error	No	Rollback resourceA and resourceB
4	Rollback	DELETE /resourceA, PATCH rollback /resourceB	200 OK	Yes	Composite operation ends with error

💡 Step 3 failed, so rollback was triggered to undo previous changes.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
resourceA_status	none	created	created	rollback started	rolled back
resourceB_status	none	none	updated	rollback started	rolled back
resourceC_status	exists	exists	delete failed	exists	exists
operation_status	pending	pending	pending	failed	failed

Key Moments - 2 Insights

Why do we rollback resourceA and resourceB after resourceC deletion fails?

Because the composite operation must keep data consistent. The execution_table shows step 3 failed, so rollback undoes previous successful steps to avoid partial changes.

What happens if the first API call fails?

The composite operation stops immediately without calling other APIs, as shown in the concept_flow where failure at API 1 leads directly to end with error.

Visual Quiz - 3 Questions

Look at the execution_table, what is the response of the PATCH /resourceB call at step 2?

A 500 Internal Server Error

B 201 Created

C 200 OK

D 404 Not Found

💡 Hint

Check the Response column in row for step 2 in execution_table.

At which step does the composite operation decide to rollback?

A Step 3

B Step 1

C Step 2

D Step 4

💡 Hint

Look at the Success? column and Action Taken for step 3 in execution_table.

If the DELETE /resourceC call succeeded, what would be the final operation_status?

A failed

B success

C pending

D rollback started

💡 Hint

Refer to variable_tracker and concept_flow where all success leads to operation end with success.

Concept Snapshot

Composite operations call multiple APIs in order.
Each step checks success before continuing.
If any step fails, rollback undoes previous changes.
This keeps data consistent across resources.
Useful for multi-resource updates in REST APIs.

Full Transcript

Composite operations in REST APIs involve calling multiple API endpoints one after another. After each call, the system checks if it succeeded. If a call fails, the system rolls back any previous successful changes to keep data consistent. For example, creating resource A, updating resource B, and deleting resource C happen in sequence. If deleting resource C fails, the system undoes the creation and update to avoid partial changes. This process ensures all-or-nothing behavior across multiple resources.