Bulk Operations API Design

Bulk operations APIs allow clients to create, update, or delete multiple resources in a single HTTP request, dramatically reducing the overhead of making hundreds or thousands of individual API calls. This is essential for data import scenarios, batch updates, and synchronization workflows. A well-designed bulk endpoint accepts an array of operations, processes them (either all-or-nothing or with partial success), and returns per-item results indicating success or failure for each operation.

The key design decision is transaction semantics: should the entire batch succeed or fail atomically (simpler but less flexible), or should each item be processed independently with per-item status codes (more useful but more complex)? Most production APIs choose the partial-success model, returning a 200 (or 207 Multi-Status) with an array of results that mirrors the input array order, each containing a status code and either the created/updated resource or an error detail.

Bulk endpoints need strict limits on batch size (e.g., max 100 items per request) to prevent timeout and memory issues. For very large batches (thousands of items), the API should accept the batch asynchronously: return 202 Accepted with a job ID, process the batch in the background, and allow the client to poll a status endpoint or receive a webhook when processing completes. Request validation should validate the entire batch before processing any items to fail fast on obviously invalid input.