PUT vs PATCH
💡 Concept Name
PUT vs PATCH – Both are HTTP methods used for updating resources in RESTful APIs. PUT replaces the entire resource, while PATCH applies partial modifications.
📘 Quick Intro
PUT requires sending a complete representation of the resource to overwrite it fully. In contrast, PATCH sends only the changes to update specific fields. Both are idempotent but serve different purposes.
🧠 Analogy / Short Story
Think of updating your résumé: using PUT is like rewriting and submitting the entire document, even if you only updated one detail. PATCH is like correcting just that one line and saving the change.
🔧 Technical Explanation
- 📦 PUT: Fully replaces the target resource with the data provided.
- 🩹 PATCH: Applies partial updates to one or more fields.
- 🧾 Payload: PUT requires the entire resource representation; PATCH only the modified attributes.
- ♻️ Idempotency: Both methods are idempotent, meaning repeating them results in the same final state.
- 🛠️ When to Use: Use PUT for full replacements, PATCH for partial modifications.
🎯 Purpose & Use Case
- ✅ Use PUT when replacing an entire user profile or configuration file.
- ✅ Use PATCH for quick edits, like updating an email or status field.
💻 Real Code Example
// PUT - full replacement
app.put('/user/:id', (req, res) => {
const user = { ...req.body, id: parseInt(req.params.id) };
res.json({ message: 'User replaced via PUT', user });
});
// PATCH - partial update
app.patch('/user/:id', (req, res) => {
user = { ...user, ...req.body };
res.json({ message: 'User updated via PATCH', user });
});
❓ Interview Q&A
Q1: What is the key difference between PUT and PATCH?
A: PUT replaces the entire resource; PATCH updates only specified parts.
Q2: Is PUT idempotent?
A: Yes, sending the same PUT request multiple times yields the same result.
Q3: When is PATCH preferable over PUT?
A: When updating a few fields without affecting the whole resource.
Q4: Does PUT require full resource data?
A: Yes, it expects a complete resource representation.
Q5: Can PATCH be used for large updates?
A: Yes, especially to avoid sending the entire resource.
📝 MCQs
Q1. Which HTTP method fully replaces a resource?
- PATCH
- PUT
- GET
- POST
Q2. Which HTTP method allows partial updates?
- GET
- PUT
- POST
- PATCH
Q3. Is PUT idempotent?
- Yes
- No
- Only for GET
- Depends on implementation
Q4. What does PATCH do?
- Deletes fields
- Replaces entire object
- Creates new object
- Updates specific fields
Q5. Which method is better for updating a single field?
- GET
- PUT
- PATCH
- DELETE
Q6. PUT requires:
- Partial data
- No data
- Complete resource representation
- Only an ID
Q7. PATCH is useful when:
- Deleting resources
- Reading metadata
- Creating new IDs
- Updating parts of a resource
Q8. PATCH is typically:
- Unsafe
- Non-idempotent
- Idempotent
- Unreliable
Q9. Which HTTP method sends heavier payloads?
- PATCH
- PUT
- HEAD
- OPTIONS
Q10. Which method overwrites an object?
- PATCH
- GET
- PUT
- POST
💡 Bonus Insight
Some APIs implement PATCH using the JSON Patch standard (RFC 6902), which defines a set of operations like add, remove, and replace. This allows precise, operation-based updates but can be more complex to handle.
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