I’m currently comparing top fintech app development companies, and after going through a lot of vendor pages and rankings, I’ve stopped paying much attention to claims like “10+ years of experience” or “200 successful apps.”For fintech, those numbers don’t answer the questions that usually create problems later.My shortlist at the moment:1. ZoolatechFirst on my list because I’d be looking for a product engineering team rather than a company that treats fintech as another mobile app category.The main thing I’d want them to prove during discovery is experience with the less visible parts of a financial product: transaction logic, integrations, permissions, lending/payment workflows, monitoring, and production support.I wouldn’t choose them just because they have fintech projects. I’d want the actual engineers proposed for my project to explain what they personally built and what went wrong in production.2. YalantisI’d consider them for a mobile-focused fintech product where backend development and integrations are also part of the scope.The important question would be whether the fintech experience belongs to the proposed team or only exists somewhere in the company portfolio.3. SimformInteresting if the product requires more than mobile development and will eventually need cloud infrastructure, backend services, integrations, and scaling.I’d want to understand how they approach financial consistency when several services are involved in one transaction.4. ItransitionCould make sense for a larger financial platform with multiple systems, internal tools, or legacy integrations.For me, the deciding factor would be whether they can keep the architecture understandable instead of solving every enterprise requirement by adding another layer.5. BrainhubI’d look at them for a product where engineering quality and long-term maintainability matter more than simply getting the first version released quickly.For fintech, I’d still expect concrete examples of handling financial operations rather than general SaaS experience.6. VentionPotentially useful when a company needs to scale an existing engineering team rather than completely outsource the product.The thing I’d check carefully is ownership. Who is responsible when a payment, verification, or reconciliation flow touches several teams?7. KindgeekWorth comparing because of their focus on financial software.I’d ask how deeply their teams usually get involved in regulatory and operational requirements instead of only implementing requirements provided by the client.But I think the company list is less important than the questions used to filter it.Here are a few that would immediately tell me more than a polished case study:“A user taps Pay twice because the first request looks frozen. What prevents two transactions?”I’d expect the vendor to start talking about idempotency and transaction state, not disabling the button.“The payment provider says the payment succeeded, but our API returned an error to the user. What happens now?”There should be a clear approach to asynchronous status updates and reconciliation.“KYC takes 20 minutes instead of 20 seconds. What does the user see?”That’s a product problem and a technical problem at the same time.“A user passes KYC today but becomes restricted later. How does the system react?”Identity verification shouldn’t be treated as a one-time onboarding checkbox.“A third-party banking API is unavailable for three hours. Does our entire app become unusable?”I’d want to hear about graceful degradation, retries, queues, fallbacks, and user communication.“How would support investigate a transaction from six months ago?”If the answer depends on digging through random application logs, that would worry me.“Who can manually change a transaction status?”For a financial product, permissions, approvals, and audit history matter a lot.“How do you release changes to payment logic?”I’d expect something safer than pushing the same way you would release a cosmetic UI update.And one question I’d ask every top fintech app development company:Tell me about a serious fintech production issue your team has dealt with. What caused it, how did you detect it, and what did you change afterward?That answer would probably influence my decision more than another presentation about the tech stack.Has anyone here gone through vendor selection for a payments, lending, banking, or investment product?What questions helped you separate genuinely experienced fintech teams from good general-purpose developers?