How to Understand Complex Financial Business Logic When Modernizing a Legacy Service?

Mid-Level Software Engineer at Taro Community3 months ago

I am currently working as a Java Developer. FYI, I am entirely new to the Java Dev ecosystem but have prior dev experience with ASP.NET MVC. My team and I are working on modernizing a financial service. We are still in the early stages of the project, still trying to understand the legacy service itself. I was given a document that explains the service's business logic, but it's heavily filled with financial jargon, which none of my teammates are familiar with. We are all tasked to go through the doc. I understand it's a complex task, but I am trying to figure out how to piece it together and contextualize everything: the scope, the input/output structure, etc. Do you have any advice on how to tackle this?

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(4 comments)

2
Bikram Kashyap
•Software Engineer @ Verily
3 months ago
This is the way I would think about it.

Learn the jargon. ChatGPT can help a lot in this. Else ask for resources

10% of the jargon will have a complicated or ambiguous meaning. Example from an old project, in healthcare, there is an open source ODM data model. We had a hard time rationalizing what a Visit is, as online visits were becoming a thing.

Look at the test cases. They can be living documentation of whats going on. P.S., see if you can arrange the tests in go's table test style, that makes understanding a lot easier.

Add input output logs to a percentage of requests in dev.

See if you can create a log with all the places the code went to. Use a threadlocal accumulator if a single request is single threaded.
2
Yogi Sharma
•Founder @ Yogi Sharma Coaching, Ex-Facebook
3 months ago
In addition to what Bikram mentioned, are there any people who have the "source of truth" -- who can explain the business logic the way it is supposed to work?

When you have that, have a fixed time to struggle with a specific challenge (a few hours to a day or two), and if you cannot figure it out, ask for help. People tend to ask for help way too late, and end up wasting a lot of time. When I worked at Facebook in early 2010s, we had a "rule of thumb" -- spend half an hour struggling with what you don't understand. If you cannot understand after that, ask around.

So, both side are important. Don't ask around without putting in the work. And don't put in too much work, because resource in terms of other people can be a lot more effective.

Happy to expand further if this is helpful. (E.g., how to actually implement it.)
0
Ammar C
•Entry-Level Software Engineer [SDE 1] at Amazon
3 months ago
In addition to the great points everyone has mentioned here, I would try to look at as many code review comments and design doc feedback comments as I could to get a better feel for the project context -> That's what these mechanisms are for.
0
Mid-Level Software Engineer [OP]
•Taro Community
a month ago
I’m currently working in govtech through Deloitte on a modernization project I really like — strong team, good scope, and solid work-life balance. But the contract’s been unstable due to DOGE and broader government uncertainty. It’s on a week-to-week renewal, and we’re all operating under the assumption that it could end at any moment.

If that happens, I’ll go on the bench at Deloitte. I’d have a few months to land something else internally, but the market is flooded — especially in government — and a lot of very experienced folks are out there looking.

I’ve got about 3 years of experience — started in .NET, now doing backend Spring Boot work. I’m confident in my ability to develop and ship features, but I know I’m still ramping up on architecture/design and Spring Boot-specific technical interview stuff.

What’s tough is I thought this role would be my launch pad — the one that helps me level up and grow into something bigger. Now it feels like I’m in limbo. I don’t want to bounce to another company just for the sake of it. If I make a move, it needs to be to a role with serious upside — higher pay (ideally $180K+), better long-term growth, and the chance to really build something meaningful.

My big question is: how do I focus and prioritize right now? I’m trying to double down on things with the highest ROI — getting sharper at development through building, Leetcode, system design, and possibly exploring something like MLOps. But honestly, I feel a bit scattered. It feels like just being a good software engineer isn’t enough anymore unless you’re already senior. Like you have to be a subject matter expert, bring business value, or have some niche.

I’m trying to realign around my actual goals: be an excellent engineer, build cool shit, make great money doing it, and still have time for a life outside of work. I don’t want to drift through my career — I want to move with purpose. So how do you figure out what to prioritize, especially when you’re pulled in so many directions?