Database Isolation Levels

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What is the purpose of database isolation?

To execute transactions in parallel
To commit transactions simultaneously
To ensure a transaction executes as if it were the only one running (correct)
To allow multiple transactions to run concurrently

What is the highest isolation level?

Repeatable Read
Read Committed
Serializalble (correct)
Read Uncommitted

In Read Committed isolation level, when can data modification be read?

During the transaction execution
After the transaction is committed (correct)
Before the transaction is committed
At the start of the transaction

What mechanism is used to guarantee isolation?

MVCC and locks (B) Signup and view all the answers

In Repeatable Read isolation, what happens to the data read during the transaction?

It stays the same as when the transaction started (B) Signup and view all the answers

What is the purpose of the roll_pointer?

To point to the old row (A) Signup and view all the answers

What type of information does the 'vmstat' command report?

Information about system processes, memory, paging, and CPU activity (C) Signup and view all the answers

What is the purpose of the 'lsof' command?

To list open files of the current system (D) Signup and view all the answers

Which caching strategy involves writing data to the system and then storing it in the cache?

Write through (A) Signup and view all the answers

What is a potential issue with uploading large files directly to an object storage service?

The network connection may fail during the upload (B) Signup and view all the answers

What is the primary purpose of the 'pidstat' command?

To monitor system resource utilization by processes (A) Signup and view all the answers

What type of information does the 'netstat' command display?

Statistical data related to IP, TCP, UDP, and ICMP protocols (A) Signup and view all the answers

What is the purpose of applying multiple hash functions in a Bloom filter?

To minimize the possibility of false positives (A) Signup and view all the answers

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 (A) Signup and view all the answers

What is the primary advantage of a solid-state drive (SSD) over a hard disk drive (HDD)?

Faster read and write speeds (C) Signup and view all the answers

What is the role of the host interface in SSD architecture?

To receive commands from the user (C) Signup and view all the answers

What is a characteristic of a good hash function for a Bloom filter?

Fast and uniformly distributed (C) Signup and view all the answers

What is the purpose of the cells in an SSD?

To store bits of data (C) Signup and view all the answers

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 (C) Signup and view all the answers

What can cause an FX discrepancy to reconcile?

Purchasing in a different currency from the bank account (A) Signup and view all the answers

What is an example of a platform-specific problem on the buyer side?

Shadow transaction from Paypal (A) Signup and view all the answers

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 (D) Signup and view all the answers

What is a result of the time and currency dimensions in a Paypal purchase?

Multiple debit/credit pairs are triggered at different times (A) Signup and view all the answers

What is the result of a shadow transaction from Paypal?

Only a partial amount of transaction B is withdrawn from the bank account (C) Signup and view all the answers

What is the primary purpose of the read replica pattern?

To improve the performance of read operations (A) Signup and view all the answers

What is the main challenge of the read replica pattern?

Data replication lag (B) Signup and view all the answers

What happens to data-modifying commands in the read replica pattern?

They are sent to the primary database (A) Signup and view all the answers

Why might Alice not see her order immediately after placing it?

Due to data replication lag (C) Signup and view all the answers

What is the purpose of 'read-after-write' consistency?

To ensure that reads immediately follow writes (D) Signup and view all the answers

What is a possible solution to mitigate the data replication lag?

Latency sensitive reads are sent to the primary database (B) Signup and view all the answers