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Availability : accessing text
Security : no one who don't have authority can't access it.
Performance : low latency for accessing the text from link
Write
DAU : 100M
text creation in a day : 1M
Read
Peak read per hour : 10M
RPS : 10M/60*60 = 10000K/3600=20K/sec
Storage
Maximum size of 1 text = 50K
storage size in a day = 50K*1M = 50GB
POST /api/text/create
GET /api/text/shareableLink
POST /api/text/modifyPermission
POST /api/user/register
POST /api/user/login
Text
Customer, link
Server store the paste to DB and redis with TTL which is from user definded expiredTime.
for fault tolerance and distributing the request efficiently we introduce CDN. If celebrity create the link for paste service will store it to CDN. And people can access to content event without reaching our server.
If people access server with link which is not in CDN. server check their permission and return the result from redis. It can reduce the load from db.
we don't need to manage the expired time for the cache since it has ttl. still we need to manage it for db. Cron job will fetch expiredtime, text id regularly. and delete it.
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...
delete expired paste vs archive
deleting expired paste has beneficial for saving cost for storage. But it lose the opportunity for anaylize and improvement for future and future support for new user's requirements.
Archiving expired paste increase the cost for storage. But we would choose this for future.
MySQL vs MongoDB vs S3
if we choose deleting expired paste, MySQL is enough for this service. But We will choose hybrid. for not expired paste we would use MySQL and for expired paste we would use S3 after archiving
we would replicate the server since it is stateless service.
DB
Multi AZ setup. and incremental backup
redis
point in recovery
cron job