Database Isolation Levels

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Questions and Answers

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?

<p>MVCC and locks (B)</p> Signup and view all the answers

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

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

What is the purpose of the roll_pointer?

<p>To point to the old row (A)</p> Signup and view all the answers

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

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

What is the purpose of the 'lsof' command?

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

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

<p>Write through (A)</p> Signup and view all the answers

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

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

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

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

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

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

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

<p>To minimize the possibility of false positives (A)</p> Signup and view all the answers

Why might a bit be set by another element in a Bloom filter?

<p>Because another element's hash value overlaps with the current element's (A)</p> Signup and view all the answers

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

<p>Faster read and write speeds (C)</p> Signup and view all the answers

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

<p>To receive commands from the user (C)</p> Signup and view all the answers

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

<p>Fast and uniformly distributed (C)</p> Signup and view all the answers

What is the purpose of the cells in an SSD?

<p>To store bits of data (C)</p> Signup and view all the answers

What is triggered by a purchase via Paypal?

<p>A debit/credit pair for the transaction and another when the money is transferred to a bank account (C)</p> Signup and view all the answers

What can cause an FX discrepancy to reconcile?

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

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

<p>Shadow transaction from Paypal (A)</p> Signup and view all the answers

What happens if transaction A is canceled or incomplete when transaction B occurs on Paypal?

<p>The money from transaction A is used to partially pay for transaction B (D)</p> Signup and view all the answers

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

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

What is the result of a shadow transaction from Paypal?

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

What is the primary purpose of the read replica pattern?

<p>To improve the performance of read operations (A)</p> Signup and view all the answers

What is the main challenge of the read replica pattern?

<p>Data replication lag (B)</p> Signup and view all the answers

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

<p>They are sent to the primary database (A)</p> Signup and view all the answers

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

<p>Due to data replication lag (C)</p> Signup and view all the answers

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

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

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

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

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