System requirements

Functional:

1. An api where external service can hit with a request to shorten the url. Provide the shortened url in response.
2. An api when hit which takes the shortened url as request and gives the actual url.
3. Now, the shortened url often are used in the browser and when they are hit on the browser they will be calling my system with the shortened url. On response of this we need to provide a redirection url to the actual site

Non-Functional:

1. 100k writes per day
2. 1M reads per day
3. High reads, Medium writes (depends on the clients if there are creating a new shortened url for every url)
4. Availability of get should be ensured.
5. Writes can be eventually consistent.
6. reads should be low latency

Capacity estimation

Assuming we have around 100K shortened urls created daily, we will need to maintain around 100K records and depending on their life which can be 30 days. We need to have 1M entries present in our database. Saving 2KB of data per entry means 6Gb data storage will be required. To make it work for a longer time we can keep it with 16gb disc space

API design

1. api: /shorten/url, request {"url": {url}, "ttl": {ttl}, "namespace": {namespace}}
2. /shortenedUrlId // get requested by browser. response will be redirection to actual url
3. /expand/shortednedUrl response : actual url

Database design

We just need to store a key value pair in the database. We can use any nosql database like mongodb, aerospike, etc. I would like to create a collection with the name shortened url mapping key would be shortened url and value would be actual url. while saving, I'll also set the ttl

It will automatically handle partitioning and sharding

High-level design

I need an api gateway for my system. I need load balancer for my system. I need a urlShortening service. The url shortening service will have a single data base. Authorization of api calls will be done at api gateway

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

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?