Batch create endpoint design in Rest API - Step-by-Step Execution

Concept Flow - Batch create endpoint design

Client sends batch create request

↓

Server receives request with multiple items

↓

Validate each item

↓

Create items

↓

Send response with created items and errors

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Client receives response

The client sends many items to create at once; the server checks each, creates valid ones, collects errors for invalid ones, then replies with results.

Execution Sample

Rest API

POST /items/batch
Body: [{"name":"A"},{"name":""},{"name":"B"}]

Response:
{
  "created": [{"id":1,"name":"A"},{"id":2,"name":"B"}],
  "errors": [{"index":1,"error":"Name required"}]
}

This example shows a batch create request with 3 items; one is invalid, so the response shows 2 created items and 1 error.

Execution Table

Step	Action	Item Index	Validation Result	Create Result	Response Part
1	Receive batch request	-	-	-	Items: [{"name":"A"},{"name":""},{"name":"B"}]
2	Validate item	0	Valid	Create item with id=1	Created: [{"id":1,"name":"A"}]
3	Validate item	1	Invalid (name empty)	Skip creation	Errors: [{"index":1,"error":"Name required"}]
4	Validate item	2	Valid	Create item with id=2	Created: [{"id":1,"name":"A"},{"id":2,"name":"B"}]
5	Send response	-	-	-	{"created":[{"id":1,"name":"A"},{"id":2,"name":"B"}],"errors":[{"index":1,"error":"Name required"}]}
6	Client receives response	-	-	-	Process created items and errors

💡 All items processed; response sent with created items and errors.

Variable Tracker

Variable	Start	After Item 0	After Item 1	After Item 2	Final
created_items	[]	[{"id":1,"name":"A"}]	[{"id":1,"name":"A"}]	[{"id":1,"name":"A"},{"id":2,"name":"B"}]	[{"id":1,"name":"A"},{"id":2,"name":"B"}]
errors	[]	[]	[{"index":1,"error":"Name required"}]	[{"index":1,"error":"Name required"}]	[{"index":1,"error":"Name required"}]

Key Moments - 3 Insights

Why do we continue processing items after finding an invalid one?

The execution_table rows 3 and 4 show that even after item 1 is invalid, item 2 is still processed to create all valid items in one request.

How does the server report which items failed validation?

Row 3 and the errors variable in variable_tracker show errors include the item index and error message, so the client knows exactly which item failed.

What happens if all items are valid?

If all items are valid, errors remain empty (see variable_tracker), and the response only contains created items without errors.

Visual Quiz - 3 Questions

Look at the execution_table at step 3, what is the validation result for item index 1?

A Invalid (name empty)

B Valid

C Skipped

D Created

💡 Hint

Check the 'Validation Result' column in row 3 of execution_table.

According to variable_tracker, what is the state of 'errors' after processing item 2?

A []

B [{"index":1,"error":"Name required"}]

C [{"index":2,"error":"Name required"}]

D [{"index":0,"error":"Name required"}]

💡 Hint

Look at the 'errors' row under 'After Item 2' column in variable_tracker.

If the second item was valid, how would the 'created_items' variable change after item 1?

A [{"id":1,"name":"A"}]

B [{"id":1,"name":"A"},{"id":2,"name":"B"}]

C [{"id":1,"name":"A"},{"id":2,"name":""}]

D [{"id":1,"name":"A"},{"id":2,"name":""},{"id":3,"name":"B"}]

💡 Hint

Refer to variable_tracker's 'created_items' row and imagine item 1 is valid but has empty name.

Concept Snapshot

Batch create endpoint design:
- Client sends multiple items in one request.
- Server validates each item individually.
- Valid items are created; invalid ones are reported with errors.
- Response includes created items and error details.
- This reduces multiple requests and improves efficiency.

Full Transcript

Batch create endpoint design lets clients send many items to create in one request. The server checks each item for validity. If an item is valid, it is created and added to the created list. If invalid, an error with the item's index and message is recorded. After processing all items, the server sends a response containing both the created items and any errors found. This approach helps clients create many items efficiently and handle errors clearly. The execution table shows each step: receiving the request, validating each item, creating valid items, collecting errors, and sending the response. The variable tracker shows how created items and errors grow after each item is processed. Key moments include understanding why processing continues after errors, how errors are reported, and what happens if all items are valid. The visual quiz tests understanding of validation results, error tracking, and variable changes. Overall, batch create endpoints improve API efficiency and error handling by processing multiple items in one go.

Practice

1. What HTTP method is typically used for a batch create endpoint in a REST API?

easy

A. DELETE

B. POST

C. GET

D. PUT

Solution

1. Step 1: Understand HTTP methods for data creation

   POST is used to create new resources on the server.

2. Step 2: Apply to batch create context

   Batch create sends multiple new items in one POST request.

3. Final Answer:

   POST -> Option B

4. Quick Check:

   Batch create uses POST [OK]

Hint: Batch create always uses POST method [OK]

Common Mistakes:

• Using GET which is for reading data
• Using DELETE which removes data
• Using PUT which replaces resources

2. Which of the following is the correct JSON format for sending multiple items in a batch create request body?

easy

A. {"name": "item1", "name": "item2"}

B. [{"name": "item1"}, {"name": "item2"}]

C. {"items": [{"name": "item1"}, {"name": "item2"}]}

D. {"item1": "name", "item2": "name"}

Solution

1. Step 1: Identify JSON array structure for batch data

   Batch create expects an object with a key containing an array of items.

2. Step 2: Match correct JSON format

   {"items": [{"name": "item1"}, {"name": "item2"}]} is a JSON object with an array of objects, which is correct for batch create.

3. Final Answer:

   {"items": [{"name": "item1"}, {"name": "item2"}]} -> Option C

4. Quick Check:

   Batch create body = JSON object with items array [OK]

Hint: Batch create body is a JSON object with an array of items [OK]

Common Mistakes:

• Using duplicate keys in one object
• Sending a single object instead of an array
• Using incorrect JSON syntax

3. Given this batch create endpoint code snippet, what will be the response if one item is invalid?

POST /items/batch
Request body: [{"name": "item1"}, {"name": ""}]

Response: 400 Bad Request
{
  "error": "Validation failed",
  "details": [{"index": 1, "message": "Name cannot be empty"}]
}

medium

A. Server crashes due to invalid input

B. All items are created, ignoring the invalid one

C. Only the valid items are created, error ignored

D. No items are created, and error details are returned

Solution

1. Step 1: Understand validation behavior in batch create

   If any item is invalid, the server should reject the whole batch to keep data consistent.

2. Step 2: Analyze the response code and message

   Response 400 with error details means no items were created and client is informed.

3. Final Answer:

   No items are created, and error details are returned -> Option D

4. Quick Check:

   Validation failure returns 400 with errors [OK]

Hint: Validation errors cause full batch rejection [OK]

Common Mistakes:

• Assuming partial success without error
• Ignoring error details in response
• Expecting server to crash on bad input

4. You wrote a batch create endpoint but clients report that sending an empty array causes a 500 Internal Server Error. What is the likely fix?

medium

A. Add validation to return 400 Bad Request if array is empty

B. Change HTTP method from POST to GET

C. Remove JSON parsing from the endpoint

D. Allow empty arrays and return 204 No Content

Solution

1. Step 1: Identify cause of 500 error on empty input

   Server likely crashes because it does not handle empty arrays properly.

2. Step 2: Implement input validation for empty arrays

   Return 400 Bad Request to inform client that empty batch is invalid.

3. Final Answer:

   Add validation to return 400 Bad Request if array is empty -> Option A

4. Quick Check:

   Validate input to avoid server errors [OK]

Hint: Validate empty input to prevent server errors [OK]

Common Mistakes:

• Ignoring empty input causing crashes
• Changing HTTP method incorrectly
• Skipping JSON parsing

5. You want to design a batch create endpoint that returns the ID of each created item and reports errors per item without failing the whole batch. Which response design is best?

hard

A. {"results": [{"id": 1, "status": "created"}, {"error": "Invalid name", "status": "failed"}]}

B. {"error": "Batch failed", "status": 400}

C. [{"id": 1}, {"id": 2}]

D. {"message": "All items created successfully"}

Solution

1. Step 1: Understand partial success reporting

   To report success or failure per item, response must include status and details for each.

2. Step 2: Match response format to requirements

   {"results": [{"id": 1, "status": "created"}, {"error": "Invalid name", "status": "failed"}]} provides per-item status and error messages, allowing partial success.

3. Final Answer:

   {"results": [{"id": 1, "status": "created"}, {"error": "Invalid name", "status": "failed"}]} -> Option A

4. Quick Check:

   Per-item status in response enables partial success [OK]

Hint: Return per-item status and errors in response [OK]

Common Mistakes:

• Failing whole batch on one error
• Returning only success without error info
• Using generic messages without details