CRUD methods (save, findById, findAll, delete) in Spring Boot - Performance & Optimization

Performance: CRUD methods (save, findById, findAll, delete)

MEDIUM IMPACT

This concept affects how quickly data operations respond and how much the UI waits for data changes, impacting user interaction speed and perceived responsiveness.

Fetching all records from a database

Spring Boot

Page<Entity> findAll(Pageable pageable) { return repository.findAll(pageable); } // fetches data in pages

Fetching data in pages reduces memory use and speeds up response time.

📈 Performance GainReduces blocking time to tens of milliseconds per page

Fetching all records from a database

Spring Boot

List<Entity> findAll() { return repository.findAll(); } // fetches all data without pagination

Fetching all records at once can overload memory and delay response, especially with large datasets.

📉 Performance CostBlocks response for hundreds of milliseconds or more depending on data size

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
Fetch all without pagination	N/A	N/A	Blocks UI update waiting for data	[X] Bad
Fetch with pagination	N/A	N/A	Allows incremental UI updates	[OK] Good
Save without check	N/A	N/A	Causes unnecessary DB writes delaying response	[X] Bad
Save with existence check	N/A	N/A	Reduces DB writes improving response	[OK] Good
Delete without check	N/A	N/A	May cause errors and wasted DB calls	[X] Bad
Delete with existence check	N/A	N/A	Avoids errors and unnecessary DB load	[OK] Good

Rendering Pipeline

CRUD methods impact the server response time which affects when the browser can paint updated content. Slow CRUD calls delay the browser's ability to update the UI.

→Server Processing

→Network Transfer

→Browser Rendering

⚠️ BottleneckServer Processing due to database query and write latency

Core Web Vital Affected

INP

This concept affects how quickly data operations respond and how much the UI waits for data changes, impacting user interaction speed and perceived responsiveness.

Optimization Tips

1Use pagination to limit data fetched in findAll methods.

2Check if an entity exists before saving or deleting to avoid unnecessary database operations.

3Avoid fetching or manipulating large data sets in a single operation to keep UI responsive.

Performance Quiz - 3 Questions

Which CRUD pattern improves user interaction responsiveness in Spring Boot?

A Using pagination when fetching records

B Fetching all records at once

C Saving entities without checking if they exist

D Deleting entities without existence check

DevTools: Network

How to check: Open DevTools, go to Network tab, perform CRUD actions, and observe request duration and size.

What to look for: Look for long server response times or large payloads indicating slow or heavy CRUD operations.

Practice

1. Which Spring Boot repository method is used to add a new entity or update an existing one in the database?

easy

A. save()

B. findById()

C. delete()

D. findAll()

Solution

1. Step 1: Understand the purpose of save()

   The save() method is designed to add a new entity or update an existing one in the database.

2. Step 2: Compare with other methods

   findById() and findAll() are for reading data, and delete() is for removing data, so they do not add or update.

3. Final Answer:

   save() -> Option A

4. Quick Check:

   Add or update data = save() [OK]

Hint: Remember: save = add or update data [OK]

Common Mistakes:

• Confusing save() with findById()
• Thinking delete() adds data
• Using findAll() to save data

2. Which of the following is the correct syntax to find an entity by its ID using Spring Boot's repository?

easy

A. repository.findById(id);

B. repository.save(id);

C. repository.delete(id);

D. repository.findAll(id);

Solution

1. Step 1: Identify the method to find by ID

   The method findById(id) is used to retrieve an entity by its ID.

2. Step 2: Check syntax correctness

   repository.findById(id); is the correct syntax. Other methods do not accept an ID to find an entity.

3. Final Answer:

   repository.findById(id); -> Option A

4. Quick Check:

   Find by ID syntax = repository.findById(id) [OK]

Hint: Use findById(id) to get one entity by its ID [OK]

Common Mistakes:

• Using save() to find an entity
• Passing ID to findAll(), which takes no parameters
• Using delete() to find data

3. Given the following code snippet, what will allUsers.size() return if the database has 3 user records?

List<User> allUsers = userRepository.findAll();
int count = allUsers.size();

medium

A. 0

B. 3

C. 1

D. null

Solution

1. Step 1: Understand findAll() behavior

   The findAll() method returns a list of all entities in the database.

2. Step 2: Count the number of records returned

   If the database has 3 user records, allUsers will contain 3 elements, so allUsers.size() returns 3.

3. Final Answer:

   3 -> Option B

4. Quick Check:

   findAll() returns all records count = 3 [OK]

Hint: findAll() returns all records as a list [OK]

Common Mistakes:

• Assuming findAll() returns null if no records
• Confusing size() with findById() result
• Thinking findAll() returns a single entity

4. What is wrong with this code snippet if it throws a compilation error?

userRepository.delete(5);

Assuming delete expects an entity object, not an ID.

medium

A. The ID must be a string, not an integer.

B. The method delete does not exist in Spring Boot repositories.

C. You must pass an entity object, not an ID, to delete.

D. You should use deleteById(5) instead to delete by ID.

Solution

1. Step 1: Understand delete method signature

   The delete method expects an entity object, not just an ID.

2. Step 2: Use correct method to delete by ID

   To delete by ID, use deleteById(id) method instead of delete(id).

3. Final Answer:

   You should use deleteById(5) instead to delete by ID. -> Option D

4. Quick Check:

   Delete by ID = deleteById(id) [OK]

Hint: Use deleteById(id) to remove by ID, not delete(entity) [OK]

Common Mistakes:

• Passing ID to delete() instead of entity
• Assuming delete() accepts ID directly
• Using wrong data type for ID

5. You want to update a user's email in the database using Spring Boot. Which sequence of repository methods correctly achieves this?

// Assume userId and newEmail are given
Optional<User> userOpt = userRepository.findById(userId);
if (userOpt.isPresent()) {
    User user = userOpt.get();
    user.setEmail(newEmail);
    // What next?
}

hard

A. Call userRepository.delete(user); then save(user);.

B. Call userRepository.findAll(); to refresh the list.

C. Call userRepository.save(user); to update the user.

D. No need to call any method; changes auto-save.

Solution

1. Step 1: Retrieve the user entity by ID

   The code uses findById(userId) to get the user object.

2. Step 2: Update the user and save changes

   After setting the new email, calling save(user) updates the database record.

3. Final Answer:

   Call userRepository.save(user); to update the user. -> Option C

4. Quick Check:

   Update data = findById + modify + save [OK]

Hint: Update entity fields then call save() to persist changes [OK]

Common Mistakes:

• Assuming changes auto-save without calling save()
• Deleting before saving to update
• Using findAll() to update a single record