FastFlowPe is a payment orchestration platform. This documentation covers integration of our unified API for payments and payouts, SDKs, and workflows

{
  "event_type": "SUBSCRIPTION",
  "subscription": {
    "id": "572764cb-7bbc-42d8-b8b2-38c9adb05121",
    "payment_mode": "UPI",
    "max_cycle": 12,
    "cycles_completed": 2,
    "interval": 1,
    "plan_interval_type": "MONTHLY",
    "plan_amount": "499.00",
    "auth_amount": "1.00",
    "plan_start_date": "2026-10-01T10:00:00+00:00",
    "plan_expiry_date": "2027-10-01T10:00:00+00:00",
    "next_billing_date": "2026-11-01T10:00:00+00:00",
    "merchant_ref_id": "MERCHANT-SUB-10001",
    "status": "SUCCESS",
    "auth_status": "AUTHENTICATED"
  }
}

{
  "event_type": "SUBSCRIPTION_TRANSACTION",
  "subscription": {
    "id": "572764cb-7bbc-42d8-b8b2-38c9adb05121",
    "payment_mode": "UPI",
    "max_cycle": 12,
    "cycles_completed": 2,
    "interval": 1,
    "plan_interval_type": "MONTHLY",
    "plan_amount": "499.00",
    "auth_amount": "1.00",
    "plan_start_date": "2026-10-01T10:00:00+00:00",
    "plan_expiry_date": "2027-10-01T10:00:00+00:00",
    "next_billing_date": "2026-11-01T10:00:00+00:00",
    "merchant_ref_id": "MERCHANT-SUB-10001",
    "status": "SUCCESS",
    "auth_status": "AUTHENTICATED"
  },
  "transaction": {
    "id": "83c89a3e-8fbf-4e82-8d49-f7ef688231b8",
    "amount": "499.00",
    "payment_mode": "UPI_RECURRING",
    "utr": "428965103247",
    "status": "SUCCESS",
    "transaction_details": {
      "merchant_ref_id": "MERCHANT-SUB-10001",
      "name": "Customer Name",
      "email": "customer@example.com",
      "phone": "9876543210",
      "payment_mode": "UPI_RECURRING",
      "upi_id": "customer@upi",
      "upi_channel": "collect",
      "authorization_amount": 1
    },
    "resp_message": "Payment successful",
    "billing_period": "2026-10-01",
    "attempt_number": 1,
    "cycle_number": 3,
    "failure_code": null,
    "remark": "CHARGE"
  }
}

FastFlowPe sends subscription callbacks as HTTP POST requests to the merchant’s configured subscription_callback_url. There are currently two merchant-facing subscription callback event types:

SUBSCRIPTION
SUBSCRIPTION_TRANSACTION

Quick ReferenceDelivery Method: HTTP POSTDestination: Merchant configured subscription_callback_urlEvent Types: SUBSCRIPTION, SUBSCRIPTION_TRANSACTIONSuccessful Delivery: Any HTTP 2xx responseMaximum Delivery Attempts: 3 total attempts for the same event

SUBSCRIPTION Event

The SUBSCRIPTION event is sent when the subscription lifecycle or mandate authorization status changes. This includes events such as:

Mandate approval
Mandate failure
Subscription pause
Subscription activation
Subscription cancellation
Subscription completion
Mandate expiry
Mandate revocation
Subscription status changes detected during polling

Initial subscription creation by itself does not currently trigger this callback.

Callback Example

{
  "event_type": "SUBSCRIPTION",
  "subscription": {
    "id": "572764cb-7bbc-42d8-b8b2-38c9adb05121",
    "payment_mode": "UPI",
    "max_cycle": 12,
    "cycles_completed": 2,
    "interval": 1,
    "plan_interval_type": "MONTHLY",
    "plan_amount": "499.00",
    "auth_amount": "1.00",
    "plan_start_date": "2026-10-01T10:00:00+00:00",
    "plan_expiry_date": "2027-10-01T10:00:00+00:00",
    "next_billing_date": "2026-11-01T10:00:00+00:00",
    "merchant_ref_id": "MERCHANT-SUB-10001",
    "status": "SUCCESS",
    "auth_status": "AUTHENTICATED"
  }
}

{
  "event_type": "SUBSCRIPTION_TRANSACTION",
  "subscription": {
    "id": "572764cb-7bbc-42d8-b8b2-38c9adb05121",
    "payment_mode": "UPI",
    "max_cycle": 12,
    "cycles_completed": 2,
    "interval": 1,
    "plan_interval_type": "MONTHLY",
    "plan_amount": "499.00",
    "auth_amount": "1.00",
    "plan_start_date": "2026-10-01T10:00:00+00:00",
    "plan_expiry_date": "2027-10-01T10:00:00+00:00",
    "next_billing_date": "2026-11-01T10:00:00+00:00",
    "merchant_ref_id": "MERCHANT-SUB-10001",
    "status": "SUCCESS",
    "auth_status": "AUTHENTICATED"
  },
  "transaction": {
    "id": "83c89a3e-8fbf-4e82-8d49-f7ef688231b8",
    "amount": "499.00",
    "payment_mode": "UPI_RECURRING",
    "utr": "428965103247",
    "status": "SUCCESS",
    "transaction_details": {
      "merchant_ref_id": "MERCHANT-SUB-10001",
      "name": "Customer Name",
      "email": "customer@example.com",
      "phone": "9876543210",
      "payment_mode": "UPI_RECURRING",
      "upi_id": "customer@upi",
      "upi_channel": "collect",
      "authorization_amount": 1
    },
    "resp_message": "Payment successful",
    "billing_period": "2026-10-01",
    "attempt_number": 1,
    "cycle_number": 3,
    "failure_code": null,
    "remark": "CHARGE"
  }
}

Subscription Object

string

Callback event type.For subscription lifecycle callbacks, this is SUBSCRIPTION.

string

Internal FastFlowPe subscription ID.

string

Payment mode used for the subscription.

integer

Maximum number of billing cycles configured for the subscription.

integer

Number of successfully completed billing cycles.

integer

Number of interval units between recurring charges.

string

Interval type configured for the plan.

string

Amount configured for each subscription billing cycle.

string

Amount used for mandate authorization.

string

Subscription plan start timestamp.

string

Subscription plan expiry timestamp.

string

Next scheduled billing timestamp.

string

Merchant-defined subscription reference ID.

string

Current lifecycle status of the subscription.

string

Current mandate authorization status.

Subscription Status Values

Status	Meaning
`CREATED`	Subscription has been created.
`PENDING`	Subscription or approval is pending.
`SUCCESS`	Subscription is active.
`HOLD`	Subscription is paused.
`CANCELED`	Subscription has been cancelled.
`COMPLETED`	All subscription billing cycles have completed.

Authorization Status Values

Status	Meaning
`PENDING`	Mandate authorization is awaiting customer or bank confirmation.
`AUTHENTICATED`	Mandate authorization completed successfully.
`FAILED`	Mandate authorization failed.
`REVOKED`	Customer revoked the mandate.
`DEACTIVATED`	Mandate expired or was disabled.

Payment Mode Values

Value
`UPI`
`NET_BANKING`
`CREDIT_CARD`
`DEBIT_CARD`

Plan Interval Values

Value
`DAILY`
`WEEKLY`
`MONTHLY`
`YEARLY`

SUBSCRIPTION_TRANSACTION Event

The SUBSCRIPTION_TRANSACTION event is sent for an individual subscription payment or mandate authorization transaction. The callback contains the subscription object together with a transaction object.

Callback Example

Select the SUBSCRIPTION_TRANSACTION tab in the response example panel to view the full transaction callback payload.

Transaction Object

string

Unique FastFlowPe transaction ID for the subscription transaction.

string

Transaction amount.

string

Payment mode used for the transaction.Example: UPI_RECURRING

string

UTR or payment reference returned for the transaction.This field may be null.

string

Current status of the subscription transaction.

object

Customer information associated with the transaction.This field may be null.

string

Human-readable payment response message.This field may be null.

string

Billing period associated with the subscription transaction.

integer

Attempt number for the transaction within the billing cycle.

integer

Billing cycle number associated with the transaction.

string

Failure code associated with the transaction.This field may be null.

string

Identifies the purpose of the transaction.This field may be null.

Transaction Status Values

Status	Meaning
`CREATED`	Transaction record has been created.
`INITIATED`	Transaction has been initiated.
`PENDING`	Transaction is awaiting final status.
`SUCCESS`	Transaction completed successfully.
`FAILED`	Transaction failed.

Normal terminal callback statuses are SUCCESS and FAILED.PSP CANCELLED payment statuses are normalized to FAILED.

Transaction Remarks

Remark	Meaning
`AUTH`	Mandate authorization payment.
`CHARGE`	Recurring subscription charge.

Nullable Transaction Fields

The following transaction fields may be null:

utr
resp_message
failure_code
remark
transaction_details

transaction_details contains the transaction’s customer information.Depending on the payment mode, it may contain sensitive payment or banking information. Merchants should store and process callback payloads securely.

Callback Headers

Subscription callbacks include:

Content-Type: application/json
User-Agent: FFP-PaymentGateway/1.0

Delivery and Retries

FastFlowPe expects the merchant callback endpoint to return an HTTP 2xx status code to consider the callback successfully delivered. If the callback does not receive a 2xx response, FastFlowPe retries delivery for the same event.

Property	Behavior
Successful delivery	Any HTTP `2xx` response
Failure condition	Any non-`2xx` response or unsuccessful delivery
Maximum attempts	`3` total attempts for the same event
Retry delay	`60` seconds by default
Retry request	The same original URL, headers, and body are reused

FastFlowPe makes a maximum of 3 delivery attempts for the same callback event.This means the initial callback plus up to 2 retry attempts.If the merchant endpoint returns an HTTP 2xx response on any attempt, the callback is considered successfully delivered and no further retries are made.

Merchant callback handlers should be idempotent because the same event may be delivered more than once when retries occur.

Callback Deduplication

SUBSCRIPTION_TRANSACTION

SUBSCRIPTION_TRANSACTION callbacks are deduplicated using:

Transaction ID
Transaction status

This prevents the same transaction status from being repeatedly delivered for the same transaction.

SUBSCRIPTION

SUBSCRIPTION lifecycle callbacks are append-only. Because of this, the same subscription status may be delivered more than once.

Do not assume that callback events will be delivered exactly once.Your callback endpoint should safely handle repeated delivery of the same event.

Recommended Merchant Handling

When receiving a subscription callback:

Accept the HTTP POST request.
Read event_type.
Handle SUBSCRIPTION and SUBSCRIPTION_TRANSACTION separately.
Process the callback idempotently.
Return an HTTP 2xx response after successfully accepting and processing the event.

Return an HTTP 2xx response as soon as the callback has been successfully accepted.If FastFlowPe does not receive a 2xx response, the same event may be retried up to the maximum of 3 total delivery attempts.

Use the internal FastFlowPe subscription ID from subscription.id to correlate callbacks with subscriptions in your system.For transaction callbacks, use transaction.id as the unique transaction identifier.

{
  "event_type": "SUBSCRIPTION",
  "subscription": {
    "id": "572764cb-7bbc-42d8-b8b2-38c9adb05121",
    "payment_mode": "UPI",
    "max_cycle": 12,
    "cycles_completed": 2,
    "interval": 1,
    "plan_interval_type": "MONTHLY",
    "plan_amount": "499.00",
    "auth_amount": "1.00",
    "plan_start_date": "2026-10-01T10:00:00+00:00",
    "plan_expiry_date": "2027-10-01T10:00:00+00:00",
    "next_billing_date": "2026-11-01T10:00:00+00:00",
    "merchant_ref_id": "MERCHANT-SUB-10001",
    "status": "SUCCESS",
    "auth_status": "AUTHENTICATED"
  }
}

{
  "event_type": "SUBSCRIPTION_TRANSACTION",
  "subscription": {
    "id": "572764cb-7bbc-42d8-b8b2-38c9adb05121",
    "payment_mode": "UPI",
    "max_cycle": 12,
    "cycles_completed": 2,
    "interval": 1,
    "plan_interval_type": "MONTHLY",
    "plan_amount": "499.00",
    "auth_amount": "1.00",
    "plan_start_date": "2026-10-01T10:00:00+00:00",
    "plan_expiry_date": "2027-10-01T10:00:00+00:00",
    "next_billing_date": "2026-11-01T10:00:00+00:00",
    "merchant_ref_id": "MERCHANT-SUB-10001",
    "status": "SUCCESS",
    "auth_status": "AUTHENTICATED"
  },
  "transaction": {
    "id": "83c89a3e-8fbf-4e82-8d49-f7ef688231b8",
    "amount": "499.00",
    "payment_mode": "UPI_RECURRING",
    "utr": "428965103247",
    "status": "SUCCESS",
    "transaction_details": {
      "merchant_ref_id": "MERCHANT-SUB-10001",
      "name": "Customer Name",
      "email": "customer@example.com",
      "phone": "9876543210",
      "payment_mode": "UPI_RECURRING",
      "upi_id": "customer@upi",
      "upi_channel": "collect",
      "authorization_amount": 1
    },
    "resp_message": "Payment successful",
    "billing_period": "2026-10-01",
    "attempt_number": 1,
    "cycle_number": 3,
    "failure_code": null,
    "remark": "CHARGE"
  }
}

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Collections

Payment Links

Fund Transfer

Refunds

Callbacks

subscription

Subscription Callback Events

SUBSCRIPTION Event

Callback Example

Subscription Object

Subscription Status Values

Authorization Status Values

Payment Mode Values

Plan Interval Values

SUBSCRIPTION_TRANSACTION Event

Callback Example

Transaction Object

Transaction Status Values

Transaction Remarks

Nullable Transaction Fields

Callback Headers

Delivery and Retries

Callback Deduplication

SUBSCRIPTION_TRANSACTION

SUBSCRIPTION

Recommended Merchant Handling

​SUBSCRIPTION Event

​Callback Example

​Subscription Object

​Subscription Status Values

​Authorization Status Values

​Payment Mode Values

​Plan Interval Values

​SUBSCRIPTION_TRANSACTION Event

​Callback Example

​Transaction Object

​Transaction Status Values

​Transaction Remarks

​Nullable Transaction Fields

​Callback Headers

​Delivery and Retries

​Callback Deduplication

​SUBSCRIPTION_TRANSACTION

​SUBSCRIPTION

​Recommended Merchant Handling

SUBSCRIPTION Event

Callback Example

Subscription Object

Subscription Status Values

Authorization Status Values

Payment Mode Values

Plan Interval Values

SUBSCRIPTION_TRANSACTION Event

Callback Example

Transaction Object

Transaction Status Values

Transaction Remarks

Nullable Transaction Fields

Callback Headers

Delivery and Retries

Callback Deduplication

SUBSCRIPTION_TRANSACTION

SUBSCRIPTION

Recommended Merchant Handling