What is the difference between CAC and LTV, and why does their ratio matter?
Assesses fundamental understanding of Digital Marketing conventions, runtime behavior, and memory/performance considerations.
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
CAC is the cost of acquiring one customer. LTV is the profit that customer generates over their lifetime. Their ratio tells you whether growth is sustainable.
I calculate CAC as total sales and marketing cost divided by new customers in a period. I calculate LTV using average revenue per account, gross margin and churn, so LTV equals average revenue per account times gross margin divided by churn rate. Using margin matters because revenue is not profit.
A healthy benchmark is LTV at least three times CAC, with payback under twelve to eighteen months. Below that, growth burns cash faster than it creates value.
The ratio also shows where to act. High CAC may mean the channel is saturated or the offer is weak. Low LTV may mean poor retention or underpricing. I track both alongside churn, because rising CAC and rising churn together are an early warning.
Candidate Response Strategy & Interview Tips
- Start with a concise one-sentence summary: Deliver a direct, confident answer first before expanding into nuances.
- Demonstrate real-world trade-offs: Discuss where this approach excels and when you would avoid it in production systems.
- Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
- Prepare for interviewer follow-ups: Technical hiring panels frequently probe deeper into concurrency, backward compatibility, or alternative libraries.