myUpchar.com Interview Questions and Answers

ReactJS and PHP based User Management Portal

Q1. DSA - to find frequency of numbers in an array
Ans. 
Use a hashmap to store the frequency of each number in the array.
• Create a hashmap to store the frequency of each number in the array.

• Iterate through the array and update the frequency in the hashmap.

• Return the hashmap with the frequency of each number.
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Q2. Default Session time in PHP
Ans. 
The default session time in PHP is 24 minutes.
• Default session time in PHP is 24 minutes

• Session time can be changed using the 'session.gc_maxlifetime' directive in php.ini file

• Session time can also be set using the 'session_set_cookie_params()' function in PHP
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Q3. SQL - Get list of duplicate emails
Ans. 
SQL query to retrieve duplicate email addresses from a table
• Use GROUP BY and HAVING clause to identify duplicates

• Select the email column and count the occurrences

• Filter the results to show only emails with count greater than 1
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Q4. React useContext
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Q5. CORS applications and how to enable it
Ans. 
CORS allows web applications to make requests to a different domain than the one it originated from.
• CORS is enabled on the server side by setting the 'Access-Control-Allow-Origin' header to specify which domains are allowed to make requests.

• Options requests are sent by the browser to check if the server allows the actual request. The server should respond with the appropriate headers.

• CORS can be configured to allow spe...read more
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Q6. How to fetch lakhs of records fast in an application?
Ans. 
Use indexing, pagination, caching, and optimized queries to fetch large amounts of data quickly.
• Utilize indexing on database columns to speed up search queries.

• Implement pagination to limit the number of records fetched at once.

• Use caching mechanisms to store frequently accessed data and reduce database load.

• Optimize queries by selecting only necessary columns and avoiding unnecessary joins.

• Consider using asynchronous ...read more
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