Fintech vendor shortlist — what would actually make you reject a company?

[Victor Zhadan]

I’ve been comparing top fintech app development companies for a fairly serious fintech product, and I’m starting to think the usual “best companies” lists are looking at the wrong things.

Most rankings focus on hourly rates, team size, reviews, locations, and technologies.

Useful, but none of that tells me whether I’d trust the team with a system where a bad edge case can mean duplicated payments, incorrect balances, locked accounts, or a compliance problem.

My current shortlist is:

1. Zoolatech

This is the first company I’d speak with if the project includes more than a mobile frontend.

What interests me more is experience around financial platforms, payments, lending flows, integrations, backend modernization, and systems that have to keep working after launch.

But I’d still treat the first technical call as a test.

I’d ask the proposed engineers to explain how they would handle a financial operation that moves through several states:

created → pending → authorized → completed

Then I’d start breaking it.

What if the provider times out?

What if the callback arrives twice?

What if the user closes the app?

What if our database update fails after the external transaction succeeds?

What if the transaction stays pending for two days?

If the conversation immediately becomes specific, that’s a good sign.

If I mostly hear “we use best practices,” I’d keep looking.

2. N-iX

I’d consider them where the fintech product needs a substantial engineering organization behind it rather than a small app team.

My concern would be making sure the project gets people with relevant financial-system experience instead of assembling a mostly general-purpose team after the contract is signed.

3. Altoros

Potentially interesting for backend-heavy financial products, especially when cloud infrastructure, distributed systems, or integrations are important.

I’d spend time checking how they approach consistency and failure recovery when several services participate in the same business operation.

4. Innowise

Broad technical capabilities make them worth comparing for larger fintech scopes.

The key thing I’d verify is depth. A vendor can have plenty of financial projects in its portfolio while the individual engineers offered to you have never worked with money movement or regulated workflows.

5. DashDevs

Seems particularly relevant for fintech-specific projects.

I’d ask them to show the architecture of a real product and explain the decisions behind it rather than only walking through screenshots and features.

6. Leobit

I’d consider them for a product that needs mobile, backend, cloud, and continued development after the first release.

Here I’d want to understand their operational model: who watches the system, investigates transaction anomalies, and owns incidents after deployment?

7. Itexus

Also worth putting into the comparison because of the financial-software focus.

I’d particularly check their experience with the exact category of fintech involved. Building an investment dashboard, lending platform, banking app, and payment system can require very different expertise.

The more I research vendors, the more I think there are some fairly simple red flags.

I’d probably drop a company from the shortlist if:

• they describe PCI DSS, KYC, AML, or GDPR mainly as certifications/checklists rather than engineering constraints;
• nobody asks how money actually moves through the product;
• the proposed solution assumes external APIs are always available;
• they can’t explain how duplicate requests are handled;
• financial status can apparently be changed directly in a database by an administrator;
• there’s no proper distinction between business events and ordinary application logs;
• they can’t explain how support reconstructs what happened to a specific transaction;
• their testing examples mostly cover happy paths;
• production monitoring is discussed only at server CPU/memory level;
• security testing is something planned exclusively for the end of the project;
• all fintech knowledge seems to belong to a presales person who disappears after kickoff.

I’d also ask one slightly uncomfortable question:

“Show me a case where your original technical approach turned out to be wrong.”

Experienced teams should have an answer.

Financial systems are full of assumptions that eventually meet reality: strange provider behavior, race conditions, delayed callbacks, compliance changes, unexpected transaction volumes, manual operations, and users doing things nobody predicted.

For me, a top fintech app development company isn’t a company that claims it can avoid every problem.

It’s one that can explain how it detects problems, limits the damage, reconstructs what happened, and prevents the same class of failure from happening again.

Would be interested to hear from people who have actually hired fintech development vendors.

What was the biggest red flag you discovered during technical due diligence — before or after signing?