How should I practice Simulate an Idempotent Refund Service Flow?

Start by reading the full statement, solve the visible examples, then compare the pattern against related DoorDash onsite interview problems in FastPrep.

Is Simulate an Idempotent Refund Service Flow associated with DoorDash?

FastPrep tags this as a DoorDash onsite interview coding practice problem when the problem catalog has that company and stage context.

Simulate an Idempotent Refund Service Flow

DoorDash● MediumFULLTIMEONSITE INTERVIEW

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Problem statement

Process operations for an order service and a refund service:

["CREATE", orderId, amount] creates an order, or reports EXISTS.
["REQUEST", refundId, orderId, amount] creates a PENDING refund when enough unreserved amount remains; otherwise it records REJECTED. Reusing a refund ID is idempotent and returns its current state.
["PROCESS", refundId, "SUCCESS"|"FAIL"] settles or releases a pending reservation. Processing a terminal refund returns its current state.
["STATUS", refundId] returns its state or UNKNOWN.
["BALANCE", orderId] returns available, refunded, and reserved, or UNKNOWN.

Status lines are exactly ORDER id STATE or REFUND id STATE; balance lines are ORDER id available=A refunded=R reserved=P.

Function

simulateRefunds(operations: String[][]) → String[]

Examples

Example 1

operations = [["CREATE","o1","100"],["REQUEST","r1","o1","40"],["BALANCE","o1"],["PROCESS","r1","SUCCESS"],["BALANCE","o1"]]return = ["ORDER o1 CREATED","REFUND r1 PENDING","ORDER o1 available=60 refunded=0 reserved=40","REFUND r1 SUCCEEDED","ORDER o1 available=60 refunded=40 reserved=0"]

The pending refund reserves funds and success converts the reservation into refunded value.

Example 2

operations = [["REQUEST","r1","missing","10"],["STATUS","r1"]]return = ["REFUND r1 REJECTED","REFUND r1 REJECTED"]

A missing order creates a terminal rejected refund for idempotent retries.

Constraints

1 <= operations.length <= 100000.
IDs are nonempty and contain no spaces.
CREATE amounts are nonnegative; REQUEST amounts parse as signed integers.
Every operation has the documented shape.