System requirements

Functional:

List functional requirements for the system (Ask the chat bot for hints if stuck.)...

1. List all the products for which an auction needs to be done
2. allow users to bid for the product
3. show the last bid price to the users
4. there should be a limit on the number of auctions
5. user should get a message saying cannot be auctioned anymore.

Non-Functional:

List non-functional requirements for the system...

System should scale

Low latency, user should get a response saying bid was succesful.

Service should always be available for bidding

System should scale when there is a sudden burst of traffic

when concurrent users are trying to bid for the same product. it should support

Capacity estimation

Estimate the scale of the system you are going to design...

500M users can use the system for auction.

System is write heavy.

API design

Define what APIs are expected from the system...

POST - v1/user/auction/product - creation an auction for the product. User creates an auction for a product

{

user_id

product_id

}

response

{

auction_id

}

Concurrent users autioning the product shoudl be handles gracefully.

Database design

Defining the system data model early on will clarify how data will flow among different components of the system. Also you could draw an ER diagram using the diagramming tool to enhance your design...

1. Shard on product_id
2. All the auctions of a particular product go to a single shard

DB attributes

product_id

auction_id

creation_date

updation_date

amount

High-level design

You should identify enough components that are needed to solve the actual problem from end to end. Also remember to draw a block diagram using the diagramming tool to augment your design. If you are unfamiliar with the tool, you can simply describe your design to the chat bot and ask it to generate a starter diagram for you to modify...

Service takes the requests from user on the product for auctions and push it to the queue. consumers pick it from the queue and write to the DB in a single batch and also updates the count into the cache. key is auction id and value is count

when client calls the service, service looks into cache to see if count > X if yes, it will throw message in real time that product is already sold.

another process runs to sort the auctions based on the amount and send a webhook notification to the user that user had won the auction.

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...

1. Server receives the request from the users and publish it to kafka.
2. Kafka topics are partitioned on product_id
3. All the auctions of a particular product go into the same partition
4. Consumer will pick the auction records and write to DB and also to cache.
5. Consumer will update the cache with the updated count. If there are multiple consumer threads, there will be a lock while doing updates on cache or atomic increment
6. Cache key is product_id. value is highest_bid and auction_time
7. kafka event payload: auction_id, product_id, bid_amount
8. consumer will also send the highest bid to gateway server which will send to all the clients.
9. gateway server will get the mapping from client connection on which client is connected to which server.
10. Clients have a persistent connection with the servers.

Trade offs/Tech choices

Explain any trade offs you have made and why you made certain tech choices...

Failure scenarios/bottlenecks

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

Future improvements

What are some future improvements you would make? How would you mitigate the failure scenario(s) you described above?