Setup

Start dir for each command is repository dir;

Dependencies

Run command to install BE dependencies:

cd api/
composer install

Run command to install FE dependencies:

cd frontend/
npm install

Run commands to start BE:

cd api/
symfony server:start

Run commands to start FE:

cd frontend/
npm start

Configure db connection in .env file, edit DATABASE_URL, then run init.sql patch (creating database is omitted because doctrine does it).

Key questions (and answers)

which characters are allowed in URL?

-> https://www.rfc-editor.org/rfc/rfc1738.txt A-Z a-z 0-9 "$-_.+!*'(),"

how many link should I be prepared to store?

1 200 000 000/month - average total visits to bit.ly a month (https://www.similarweb.com/website/bit.ly/) that'd be 720 000 000 000 in 50 years? (for some reasons longlasting links would be nice) would say: 10^12

how long link should be?

Given I have 62 characters allowed to use and I need 10^12 slots, then I have 62^X = 10^12, where X is length of our link (the random part). Then X is 6.6949652078. Bit.ly uses 7 chars so I guess they are pretty familiar to that math :D I think it's reasonable, especially that 6 (one less) allowed chars for 62 chars gives 56 800 235 584, which is ~5% of an estimated number of sorts.

how generate random links and avoid duplications?

Commonly used solution is base convertion. Based on selected characters I implemented ShortUrlGenerator with BASE62_ALPHABET.