System requirements

Functional:

1. Earn points or awards for transaction
2. Redeem points at checkout for discounts, gift cards or offers
3. Manage Points
4. Custom choosable rewards
5. Track user activities as part of rewards program

Non-Functional:

1. Low-latency
2. Availability
3. Usability
4. Security
5. Scalability

Capacity estimation

Need to keep track of each user transaction, at least transaction count - increase points for it. Need storage for reward details. 1M transaction per day

Write request per ssec = 1M/10^5 = 10 RPS

Storage 1M * 100 bytes = 100 MB per day

3GB per month

API design

• GET /rewards

Lists all the rewards/points earned

• GET /reward/history

List the history of transactions which shows rewards earned and redeemed

• POST /reward/earned
• POST /reward/redeem

Database design

Rewards

• reward_id
• Reward_name
• reward_value
• expiry

Activity_tracker

• User_id
• Reward_id
• order_id:
• timestamp:
• Expiry:
• Action: 1 - received, 0- redeemed

User_wallet

• User_id
• Wallet_id
• Current_balance:

High-level design

1. Reward Management Service
2. Order Reward Manager - track activity for which points are eared, or redeemed
3. Reward wallet Service

Reward Management Service: 

1. Central places to manages the rewards
2. This service holds a set of rules related to the rewards program. For example: 
3. For a food order of value between S$20-40 - points earned = 2

Food order S$40-60 - 4 

>S$60 - 6

Taxi order $S20-50 - 3 

1. Some rules like this. So that a transaction is made in the system its checked against the rules and points are incremented.
2. This hold a default value if no rule matches

Order Reward Manager:

After successful transaction, the transaction details are passed to this service, which talks to rule engine, calculates the points earned and logs an entry in activity tracker. In case of redemption, that transaction is also logged.

Reward Wallet Service:

Updates the wallet with most recent value based on activity.

Request flows

Explain how the request flows from end to end in your high level design. Also you could draw a sequence diagram using the diagramming tool to enhance your explanation...

Detailed component design

Dig deeper into 2-3 components and explain in detail how they work. For example, how well does each component scale? Any relevant algorithm or data structure you like to use for a component? Also you could draw a diagram using the diagramming tool to enhance your design...

Trade offs/Tech choices

1. How do we ensure real-time experience for user

We can increase latency by - caching the rewards rules and accessing from cache.

We can even write the rewards earned to cache and then update in DB.

Failure scenarios/bottlenecks

Try to discuss as many failure scenarios/bottlenecks as possible.

Future improvements

1. Gift share with points earned.
2. Auto redemption for rewards associated with the product.