How is Zhihu's database designed?

how is Zhihu"s database designed?
what I don"t understand is how Zhihu"s questions and concerns are designed?
agree with the answer, focus on the question, and how is it stored?

Mongodb sql mysql
Jun.05,2022 
 
zan_cnt count  uid id
follow_cnt count   uidid

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MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1c13dfd-153e6.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1c13dfd-153e6.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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