Design product pages with rewarded share links
PremiumBackend systemMedium
- Share link tracking
- Every nth clicker reward
- Atomic counters
Quick answer
This backend system interview question asks you to design product pages with rewarded share links. Aim for a design that meets its requirements at the stated scale, then explain its main components, data flow and trade-offs. Interviewers want to see how you scope the problem, size it and defend each choice.
The problem
Design product pages with rewarded share links: any shopper can create a trackable share link for a product page, like the referral links on large online stores, and every Nth unique person who clicks wins a voucher. The hard part is numbering clickers exactly once under viral traffic while redirects stay fast.
Companies list product pages and run a reward campaign on a page: they choose N, a voucher budget and dates. All share links for that page feed one campaign count. Sharers and companies watch how each link performs.
What must the system do?
- Reward every Nth clicker: Valid clicks in a campaign are numbered 1, 2, 3 and so on; each clicker whose number is a multiple of N wins one voucher, until the budget runs out.
- Redirect and record: A click redirects to the product page and records time, link, user, country, device and referrer.
How well must it do it?
- Exact rewards: Each multiple of N gets exactly one voucher, no user gets two numbers in one campaign, and vouchers never exceed the budget.
- Fast redirects: Under 50 ms at p99 at the server, and redirects keep working when counting or analytics is down.
What scale should you design for?
Use these numbers in your estimates.
The scale numbers unlock with this questionUnlock
Key concepts
- Share link tracking
- Every nth clicker reward
- Atomic counters
- Click deduplication
- Idempotent voucher issuing
- Link analytics
How you’ll practise
- Requirements
- Estimate
- API and data
- High-level design
- Deep dives
- Wrap-up
Lala, personalized to you, gives a hint when you ask and reviews your design when you are ready.
What do interviewers look for?
In any backend system design round.
- Clarifies the requirements before drawing anything
- Uses a few numbers that actually change the design
- Draws a clear path from the client to storage
- Picks storage and caching with reasons, not by habit
- Explains what breaks first under load and how to fix it
- States trade-offs openly instead of claiming a perfect design
Questions people ask about this interview question
- Which design type is this question?
- It is a backend system question. You design product pages with rewarded share links and explain your choices the way you would in an interview.
- Is this question asked at entry level?
- It is marked Medium. Entry-level engineers can practise it, but it expects you to reason about requirements and trade-offs, not only list components.
- What should I cover first?
- Start with the requirements: what the system must do, how well it must do it and which numbers change the design. Agree on scope with the interviewer before you design anything.
- Can I practise it for free?
- It is a premium question. Sign up and unlock it once for 10 credits; it then stays unlocked. When you finish, Lala, your personalized AI mentor, can review your design for 30 credits.
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Updated · Written by the SevyDevy team