30 Questions
What is the purpose of database isolation?
To ensure a transaction executes as if it were the only one running
What is the highest isolation level?
Serializalble
In Read Committed isolation level, when can data modification be read?
After the transaction is committed
What mechanism is used to guarantee isolation?
MVCC and locks
In Repeatable Read isolation, what happens to the data read during the transaction?
It stays the same as when the transaction started
What is the purpose of the roll_pointer?
To point to the old row
What type of information does the 'vmstat' command report?
Information about system processes, memory, paging, and CPU activity
What is the purpose of the 'lsof' command?
To list open files of the current system
Which caching strategy involves writing data to the system and then storing it in the cache?
Write through
What is a potential issue with uploading large files directly to an object storage service?
The network connection may fail during the upload
What is the primary purpose of the 'pidstat' command?
To monitor system resource utilization by processes
What type of information does the 'netstat' command display?
Statistical data related to IP, TCP, UDP, and ICMP protocols
What is the purpose of applying multiple hash functions in a Bloom filter?
To minimize the possibility of false positives
Why might a bit be set by another element in a Bloom filter?
Because another element's hash value overlaps with the current element's
What is the primary advantage of a solid-state drive (SSD) over a hard disk drive (HDD)?
Faster read and write speeds
What is the role of the host interface in SSD architecture?
To receive commands from the user
What is a characteristic of a good hash function for a Bloom filter?
Fast and uniformly distributed
What is the purpose of the cells in an SSD?
To store bits of data
What is triggered by a purchase via Paypal?
A debit/credit pair for the transaction and another when the money is transferred to a bank account
What can cause an FX discrepancy to reconcile?
Purchasing in a different currency from the bank account
What is an example of a platform-specific problem on the buyer side?
Shadow transaction from Paypal
What happens if transaction A is canceled or incomplete when transaction B occurs on Paypal?
The money from transaction A is used to partially pay for transaction B
What is a result of the time and currency dimensions in a Paypal purchase?
Multiple debit/credit pairs are triggered at different times
What is the result of a shadow transaction from Paypal?
Only a partial amount of transaction B is withdrawn from the bank account
What is the primary purpose of the read replica pattern?
To improve the performance of read operations
What is the main challenge of the read replica pattern?
Data replication lag
What happens to data-modifying commands in the read replica pattern?
They are sent to the primary database
Why might Alice not see her order immediately after placing it?
Due to data replication lag
What is the purpose of 'read-after-write' consistency?
To ensure that reads immediately follow writes
What is a possible solution to mitigate the data replication lag?
Latency sensitive reads are sent to the primary database
Test your understanding of database isolation levels, including Serializable, Repeatable Read, Read Committed, and Read Uncommitted, and how they handle concurrent transactions.
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