Software Engineer Interview Prep Podcast
May 17, 2026 · 10 min · 12 segments
Design a batch processing system for end-of-day payment settlement at a payments company that processes **50 million transactions per day**. The system must net merchant positions, calculate fees, and…
Whether you're a senior software engineer candidate right now or you're aiming to be one soon, this is exactly the kind of grueling, deceptively complex scenario that really separates the novices from the heavyweights.
Picture this: you walk into the room, sit down, and the interviewer just stares you down and drops this prompt: "Design a batch processing system for end-of-day payment settlement.
Walk me through your design, covering reliability, scalability, and how you're gonna handle failures." I mean, on the surface, it sounds kinda simple, right? Just a batch job.
But make no mistake, this is a total trap.
It's actually a deep dive into distributed systems durability, exactly once-ish semantics, and handling heavily constrained downstream partners.
Because here is the real kicker.
You're designing for a massive scale of fifty million transactions per day.
Think about that.
At an average of, say, twenty-five bucks a transaction, we're talking about one point two five billion dollars, literally billion with a B, flowing through your system every single day.
When you're dealing with that much money, the whole idea of eventual consistency suddenly feels a lot less comforting, doesn't it? Okay, let's dive into this.
Whether you're a senior software engineer candidate right now or you're aiming to be one soon, this is exactly the kind of grueling, deceptively complex scenario that really separates the novices from the heavyweights.
Picture this: you walk into the room, sit down, and the interviewer just stares you down and drops this prompt: "Design a batch processing system for end-of-day payment settlement.
Walk me through your design, covering reliability, scalability, and how you're gonna handle failures." I mean, on the surface, it sounds kinda simple, right? Just a batch job.
But make no mistake, this is a total trap.
It's actually a deep dive into distributed systems durability, exactly once-ish semantics, and handling heavily constrained downstream partners.
Because here is the real kicker.
You're designing for a massive scale of fifty million transactions per day.
Think about that.
At an average of, say, twenty-five bucks a transaction, we're talking about one point two five billion dollars, literally billion with a B, flowing through your system every single day.
When you're dealing with that much money, the whole idea of eventual consistency suddenly feels a lot less comforting, doesn't it? Okay, let's dive into this.
The rest of this transcript — segmented and speaker-labeled, so you land on the exact moment something was said
Search every transcript — by keyword, by phrase, or by meaning, across every show Radar indexes
Trends — what is surging across podcasts, measured against its own baseline
Alerts — when a name you follow appears in a newly indexed episode
No account is needed to search Radar.