AWS मा load balancing कसरी काम गर्छ?

Question

Accepted Answer

**Elastic Load Balancing (ELB)** ले आने traffic लाई multiple targets (EC2 instances, containers, आदि) मा वितरण गर्छ — **availability** (कोनै पनि single point of failure नहुने) र **scalability** (load फैलाने) को सुधार गर्दै। यो reliable, scalable applications को लागि एक मुख्य component हो।

## Load balancer ले गर्ने काम

```text
A LOAD BALANCER sits in front of multiple backend targets and distributes requests:
  Client → LOAD BALANCER → ┬→ Instance 1
                           ├→ Instance 2
                           └→ Instance 3
  → spreads traffic across targets (scalability + no single instance overloaded)
  → HEALTH CHECKS: routes only to HEALTHY targets (an unhealthy one is bypassed)
  → if a target fails, traffic goes to the others → HIGH AVAILABILITY
  → single entry point (clients hit the LB, not individual instances)
```

## AWS load balancers को प्रकार

```text
APPLICATION LB (ALB) → Layer 7 (HTTP/HTTPS): content/path/host-based routing,
  great for web apps, microservices, containers (route /api → one group, /app → another)
NETWORK LB (NLB) → Layer 4 (TCP/UDP): ultra-high performance, low latency, static IPs
GATEWAY LB → for deploying virtual network appliances
(Classic LB → legacy)
→ ALB is the common choice for HTTP applications.
```

## मुख्य विशेषताहरु

```text
✓ HEALTH CHECKS — detect unhealthy targets and stop routing to them (reliability)
✓ Spread across MULTIPLE AZs — survive an AZ failure
✓ Works with AUTO SCALING — automatically includes new instances as they scale
✓ SSL/TLS termination (handle HTTPS at the LB)
✓ Sticky sessions, path/host routing (ALB), WebSocket support
```

## किन यो महत्वपूर्ण छ

Load balancing बुझ्नु मूल्यवान छ किनभने यो AWS मा **reliable र scalable** applications निर्माण गर्नको लागि एक मुख्य component हो, त्यसैले यो महत्वपूर्ण practical ज्ञान हो।

Load balancer दुई आधारभूत आवश्यकता पूरा गर्छ: **availability** (multiple backend targets मा traffic वितरण गर्दै **health checks** को साथ जो केवल healthy targets मा traffic पठाउँछ, त्यसैले एक instance विफल भएमा, traffic अन्यलाई जान्छ — single points of failure हटाउँछ) र **scalability** (multiple instances मा load फैलाउँदै ताकि कोनै पनि एक overloaded नहोस्, र एकल entry point प्रदान गर्दै)।

यसले load balancing लाई कुनै पनि application को लागि जो significant traffic को साथ reliable तरिकामा सम्भाल्न आवश्यक छ, अत्यावश्यक बनाउँछ।

**Types** बुझ्नु — **Application Load Balancer (ALB)** Layer 7 HTTP/HTTPS को लागि content/path/host-based routing को साथ (web applications र microservices को लागि सामान्य विकल्प), **Network Load Balancer (NLB)** Layer 4 ultra-high-performance TCP/UDP को लागि — सही विकल्प चयन गर्न मद्दत गर्छ।

**मुख्य विशेषताहरु** बुझ्नु महत्वपूर्ण छ: health checks (reliability को लागि), multiple AZs मा फैलाउँदै (AZ failures को बाचिरिकरण, high-availability pattern को साथ संयोजन), **auto scaling** को साथ integration (automatically नयाँ instances समावेश गर्दै जब तिनीहरु scale गर्छन् — त्यसैले load balancing र auto scaling एक अर्कासँग elastic, resilient applications को लागि काम गर्छन्), र SSL/TLS termination।

Load balancing + auto scaling + multi-AZ deployment को संयोजन scalable, highly-available AWS applications को लागि foundational pattern हो।

Kinaकि reliable, scalable applications लाई multiple instances मा traffic वितरण गर्न आवश्यक छ (availability र scale को लागि), र ELB (यसको types, health checks, multi-AZ spread, र auto-scaling integration को साथ) यो mechanism हो, load balancing बुझ्नु मूल्यवान, practically-महत्वपूर्ण AWS ज्ञान हो — resilient cloud architecture को एक core component जो auto scaling र multi-AZ deployment को साथ काम गर्दै applications निर्माण गर्न जो real-world traffic लाई reliable र scale मा सम्भाल्छ।