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Idempotency keys

Increase's APIs include an optional creation parameter called the Idempotency-Key. This string parameter should be a unique value you pre-allocate in your system before invoking the creation method. For example, you could use your application's Invoice ID for an ACH Transfer or your application's User ID for an Entity.

We recommend setting the value for all POST requests. The value should be transmitted as the HTTP header Idempotency-Key.

You cannot re-use an Idempotency-Key across two objects—passing Idempotency-Key guarantees that at most one object is created per key. If Increase receives a second request with the same arguments and Idempotency-Key, we will return the object created during the first request.

Attempting to create a second, different, object with an already used Idempotency-Key will result in an HTTP 409 Conflict error with the type field set to idempotency_key_already_used_error and the resource_id set to the ID of the Object that is associated with that key.

Idempotency keys are only used for POST requests. PATCH, GET, and DELETE endpoints are inherently idempotent.

You can retrieve objects by their Idempotency-Key, too. Each list endpoint has an optional filter parameter idempotency_key. Passing an idempotency_key there will return an empty list, if that key is unused, or a list containing exactly one matching result.

Recovering from errors

You can use the Idempotency-Key header to automatically and safely retry ephemeral errors. As long as the Idempotency-Key is set to the same value and the request is valid, we will eventually return a successful object to you. We recommend building support for automatic retries, especially for important endpoints like transfer creation.

We do not recommend building automatic solutions using reads of the list endpoint: instead retry your requests with the same parameters and the same Idempotency-Key and rely on idempotency to eventually deliver you a successful response.


On the first successful request, Increase creates the Account Transfer.

curl -X POST -H "Idempotency-Key: test_001" -d $'{ "account_id": "account_1", "destination_account_id": "account_2", "description": "My great transfer!" }' 200 OK { "id": "account_transfer_abc123", "idempotency_key": "test_001" // ... }

On the second request with the same idempotency_key, Increase returns the same object.

curl -X POST -H "Idempotency-Key: test_001" -d $'{ "account_id": "account_1", "destination_account_id": "account_2", "description": "My great transfer!" }' 200 OK { "id": "account_transfer_abc123", # The same ID! "idempotency_key": "test_001" // ... }

If an idempotency key is re-used for different request arguments, the POST will fail.

curl -X POST -H "Idempotency-Key: test_001" -d $'{ "account_id": "account_1", "destination_account_id": "account_2", "description": "A different description" }' 409 Conflict { "status": 409, "type": "idempotency_key_already_used_error", "title": "The idempotency key submitted has already been used. Fetch the created object or use a different idempotency key.", "detail": null, "resource_id": "account_transfer_abc123" }

You can also access the object with the list endpoint.

GET 200 OK { "data": [ { "id": "account_transfer_abc123", # The same ID! "idempotency_key": "test_001" // ... } ] }

Deprecation notice

Prior to 2024, this functionality was only available on a subset of requests and was called unique_identifier. Learn more about the older implementation.