Implement a GPU credit allocation manager: issue credits, track usage, enforce limits and expiry.
OpenAI's signature build screen: a credit ledger that issues GPU-hours, spends them, and lets unused grants lapse in issue order. The trap is charging against the right grant first. Here is the FIFO-by-expiry design that holds up through every follow-up.
Updated Sep 2026 · Grounded in real GenAI, LLM, and AI/ML engineering interview loops and written to a senior-engineer editorial bar.
OpenAI's signature build screen: a credit ledger that issues GPU-hours, spends them, and lets unused grants lapse in issue order. The trap is charging against the right grant first. Here is the FIFO-by-expiry design that holds up through every follow-up.
Lead with where the obvious approach breaks, because that is the judgment they are screening for — most candidates jump straight to the happy path and lose the room.
Then walk the failure back through the pipeline in order, naming the one metric the customer's exec sponsor actually cares about before you propose the fix.
