Detailed Component Design

Service URL Shortener

The services are using .NET and and following the Clean Architecture, creating a possible expansion of It. The integration with other services will be made using Circuit and retry policy.

Every data inserted into the database will be available on cache for 5 minutes, after that time only the most accessed url will be there for a long term following some internal rules.

Before the service GET a data from Dynamo, It will query the cache and if needed the service will create a new cache record on redis.

When the GET route be requested It will return an status code known as 302 because it give to the requesting client browser temporarily the information of redirect, the 301 status code gives the information of permanent redirection, and this action increase the complexity of understanding the analytics data.

Background refresh - Cache TLL Handler

The service can have a algorithm to refresh the cache that is approaching the TTL deadline. But It can create a race condition to refresh that data.

The way to solve this is creating a new service worker to update the TTL proactively. This service can get a dictionary of cached data created on redis by the shortener url.

This cache can runs every 10 seconds and update all TLLs foun in the dictionary which are under 30 seconds to expire, increasing them to 300 seconds further.

This service will be a Lambda Function witten in c# .NET.

Id Generator

Base62 is built with 0-9, a-z, A-Z. It is 62 characters ^ 2.

100 millions of Shortened URL mean that I will need 100 million of Ids a day.

100.000.000 * 365 = 36,500 billion a year, but a 62^7(characters) will provide 3,5 trillion, It is much more than needed for a whole year and provide Ids for over 10 years.

I Will write the Id in dataBase only after handle a conversion behavior to avoid dicoverable url Ids.

So The architecture will use Redis Cluster incremental Id to generate Ids that is after 14 million (that is harder to be discovered) . The Redis cluster will generate unique Id even in race condition, because It creates a queue of incremental numbers. This will be used as a system to generate Id to alll the services running in the LoadBalance.

DataBase Service Shortener URL Dynamo DB

Dynamo provides high availability, low latency and good performance on high throughput and massive reads and writes because It can scale horizontally.

100 millions / 24 / 60 / 60 = 1160 Write Per Second

if a url has 100 character or 100 bytes, it will has: 9.31 GB of data a day (100 bytes × 100.000.000)

I will need at least 3.6 Terabytes of disk to live through a year.

Usually for each 1 write there are 10 reads, so 1160 * 10 = 11.600 RPS

Table named as TableShortner

Columns

PK ShortCode (text)

long_url (text)

created_at (timestamp)

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Submissions

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