Before you hire a fintech software development company to build or take over a trading or investing product, ask them eight things: where each number on the screen comes from, how they keep market data current, how they test changes that touch money, how access and sensitive data are handled, how the platform behaves when a data provider fails, how they ship without breaking what users rely on, whether one team owns the backend and the front end, and who maintains the platform after launch. A partner who answers these clearly, with examples from a platform they have built, is far less likely to hand you screens that disagree with each other.
This guide is for founders and product leaders running, or about to build, a fintech product on Ruby on Rails: trading tools, portfolio tracking, market insights, or paid education next to the tools users trade with. For the data side in more depth, see Fintech on Rails: real-time market data without stale screens.
1. Where does each number on the screen come from?
Ask them to explain, for a price, a position and a portfolio value, which system owns it and how it reaches the user. A good answer names one clear source for each kind of data and shows how every screen reads from it. If different pages calculate the same figure in different places, users will eventually see two different numbers and stop trusting the product.
2. How do they keep market data current?
Ask how prices and updates arrive: streaming connections, polling, or both, and how often. Then ask what the user sees when data is late. Look for timestamps or a clear stale state instead of an old price shown as if it were live, and for caching that is explained rather than assumed.
3. How do they test changes that touch money?
Anything that calculates a balance, a profit and loss figure, a fee or a subscription charge needs tests that run on every change. Ask to see how they test calculations, rounding and currency handling, and whether those tests block a release when they fail. Floating-point arithmetic for money is a warning sign.
4. How do they handle access and sensitive data?
Ask how roles and permissions work, how one user is kept from seeing another user's portfolio, how API keys and credentials are stored, and what is logged. If the product stores card details or connects to brokerage or bank accounts, ask which obligations apply (for example PCI DSS for card data) and how they keep that data out of systems that do not need it.
5. What happens when a data provider fails?
Every market data or third-party API goes down or slows down at some point. Ask how the platform behaves when it does: do jobs retry safely, do users see a clear message, and does anyone get alerted? Calls to outside providers belong in background jobs and one integration layer, not scattered through controllers, so a provider problem stays contained.
6. How do they ship without breaking what users rely on?
Users of a trading or portfolio product notice every regression. Ask how work is released: small, reviewable increments, a staging environment with realistic data, feature flags for risky changes, and a way to roll back quickly. "We test it before launch" is not a release process.
7. Does one team own the Rails backend and the front end?
Many fintech products are a Rails backend with a React front end. When separate vendors own each side, every feature needs a handoff and bugs fall between them. Ask who owns the APIs, who owns the screens, and who is accountable when a number is wrong.
8. Who maintains the platform after launch?
Market data sources change, APIs are versioned, and Rails releases reach end of support. Ask whether they will monitor, maintain and extend the platform, and make sure you own the code, the infrastructure accounts and the documentation, so another team could take over if needed.
Building or fixing a fintech product? Bring the current setup to a Systems Discovery Call and we will tell you what to build or fix first.
Red flags
- No clear answer to where prices, trades and portfolio values come from.
- Old prices shown as live, with no timestamp or stale state.
- Money calculated with floating-point numbers and no tests.
- Third-party API calls made inside web requests with no retries or alerts.
- Separate vendors for the backend and the front end with no single owner.
- A proposal to rebuild a working product from scratch before anything is audited.
How we work
We build new fintech platforms on Rails and React, take over existing ones, and own them long-term. Market data, trades, and portfolios come from clearly owned sources and stay consistent across every screen, and the same engineers own the Rails backend, the APIs, and the React front end. For an existing product we review the codebase first; for a new one we map data sources, accounts, and the first release, then ship working features in small, reviewable increments. Crypto WZRD, a trading and education platform we engineered, combines market insights, actionable trading setups, portfolio tools, and structured educational resources across crypto, forex, and stock markets, built with Ruby on Rails, React, and real-time APIs. We also engineered RevBits, a cybersecurity platform on Rails and React. Details are on our fintech software development page.
Common questions
Is Ruby on Rails a good fit for fintech software?
For trading tools, portfolios, accounts, subscriptions and content, yes. Rails handles the application, accounts and background jobs well, and real-time data can be delivered through API integrations and live updates. What matters more than the framework is clear data ownership, tested calculations and careful handling of sensitive data.
Should we rebuild our fintech product or take it over?
Usually take it over first. An audit shows what is fragile and what is sound, and most problems can be fixed in increments while users keep trading. See Taking over a Rails app from a previous developer: the first 30 days.
What should the first conversation cover?
Your users, your data sources, where current numbers disagree or arrive late, and what the platform must do next. A good partner leaves you with a clear picture of what to build or fix first.
Next step
If you are building a fintech product or your current platform has outgrown the way it was built, book a Systems Discovery Call. It is 45 minutes on your product, and you leave with a clear picture of what to build or fix first, whether you hire us or not.
Farooq Ch
Oct 2026