Indian payment gateways are broadly reliable and they are not perfectly reliable, and the failures cluster in the worst possible places: during a festive sale, at the end of the month, on the day a campaign lands. A business whose checkout can only route through one provider has accepted that its revenue stops when that provider has a problem. For anything past a modest volume, a second gateway is not sophistication, it is ordinary continuity planning.
Building for two starts with an abstraction, and it needs to be your own rather than a gateway's SDK. Define your internal notion of a payment attempt — amount, currency, method, customer, order — and translate to each provider behind that boundary. The moment gateway-specific fields or webhook shapes leak into your order logic, adding a second provider becomes a rewrite rather than an implementation.
Routing rules are where the value is, and they are business rules rather than technical ones. Route by method, because gateways differ in their strength across cards, UPI and net banking. Route by cost, since your negotiated rates differ per instrument. Route by success rate observed over the last hour, which is the most useful signal you have and the one nobody measures. And route away from a provider that is failing, automatically, rather than waiting for someone to notice.
That automatic failover needs care to avoid making things worse. A retry on a second gateway after an ambiguous outcome on the first is how customers get charged twice. The rule is that failover applies to attempts that definitively failed or never reached the provider, never to attempts whose outcome is unknown. Anything unknown must be resolved by querying the original provider's status API before any further action — which means your payment state model needs unknown as a first-class state, distinct from failed.
Reconciliation gets harder and more important with two providers. Each settles on its own cycle, with its own fee structure netted out, in its own file format. You now need a daily reconciliation per provider, plus a view across both that ties every order to exactly one successful payment. Without it, the duplicate charge that failover eventually causes will be discovered by the customer rather than by you.
One commercial note worth having in mind. A second gateway is also negotiating leverage: a provider who knows they carry a hundred per cent of your volume prices differently from one who knows they carry sixty. The engineering work pays for itself in continuity, and it pays for itself again in the rate conversation — which is the argument to use if the project needs justifying to someone counting the build cost.
