Payment gateway API integration — who covers the cost and ongoing maintenance?

If they're writing a custom API, the agency must commit to two core things: 1) Using idempotency keys (so a customer clicking the button twice doesn't get double-charged). 2) Queueing webhook notifications. Skip these safeguards, and whenever a connection drops, the customer gets charged but no order is created on your site.

Before signing anything, test the payment gateway's off-the-shelf module yourself to see if it actually handles your installment requirements. Agencies sometimes turn a 2-hour plugin install into a "custom API project" just to pad the invoice.

In the Mexico City market, 35.000 MXN is pretty much the upper limit for a custom API integration. We paid 28.000 MXN for a similar corporate integration last fall, and that included a 3-month technical support warranty.

Get an explicit clause added to the contract: "Software bugs resulting from the integration will be resolved by the contractor free of charge for 90 days following the go-live date." That protects you from surprise bills during the first few weeks.

With hourly maintenance deals, you risk the agency billing you hourly just to fix their own broken code. If you don't draw a hard line between bug fixes and new feature requests, you'll be stuck paying 850 MXN every single month.

sucks that this wasn't brought up on day one but payments are the backbone of the site.. and paying up front for a clean, custom API instead of hacking together a cheap pre-built plugin saves you from lost revenue down the line.

Bottom line: asking for extra budget for a custom API is normal, but don't commit to that maintenance fee right away. Lock down a 90-day warranty first, put the token-based architecture in writing, and make double-charge protection a requirement.

I think differently. honestly everyone rushing into payment API integration gets stuck at the same point.

This is my opinion, Im not claiming its absolute truth.

We got stuck at the same point for a while. Don't hesitate to ask; those who don't ask always pay more.

Good luck with that.

Do you think this works at any scale? When making a decision, first look at what data you have on hand.

You're right, I've been down that road too. Don't hesitate to ask; those who don't ask always pay more.

That's all, sorry if I went on too long.

Let me summarize what's been said so far. Any unwritten clause becomes a point of disagreement later, as both sides remember it differently.

When we decide without measuring, we always end up in the same place. Just leaving this note, it might be useful.

I have an objection here. If you don't write this down from the start, it leads to arguments later.

Just leaving this note it might be useful.

There's a trap here let me mention it. The biggest time-waster for us was not knowing who had the final say.

The biggest time-waster for us was not knowing who had the final say.

I have no experience with payment API integration, so I'm asking. Everything goes well for the first three months; problems arise in the fourth.

People defend habits not processes. Resistance comes from there.

I felt relieved reading this answer, so it's not just me. Code without setup documentation isn't yours, even if you have it.

Proven by experience.

Let me share what happened to me; it might be useful. The cheapest quote is usually the least thought-out one.

Good luck with that.

Timely topic.