AWS ALB/ELB Load Balancing Setup for High-Load Websites

AWS ALB/ELB Load Balancing Setup

Website crashing under load? 502 errors during peak promotional traffic? We've encountered this in projects with 100k+ RPS. Load balancing with AWS ALB is the standard solution for high-load projects. We configure ALB/ELB turnkey: target groups, listener rules, SSL, Auto Scaling integration. 7+ years of experience, 50+ configured load balancers. Proper ALB configuration is critical for site availability and speed — significant infrastructure savings with competent tuning.

AWS provides managed load balancers without needing to maintain your own server. Application Load Balancer (ALB) works at HTTP/HTTPS level with routing by path and headers. Network Load Balancer (NLB) — L4 TCP/UDP with minimal latency. Classic ELB is deprecated and not recommended for new projects.

Why Choose ALB over NLB?

ALB is better than NLB for HTTP/HTTPS: it supports intelligent routing, WAF integration, and static content delivery. NLB is indispensable for TCP services requiring static IPs and minimal latency. If you have a React/Vue web application or Node.js API — choose ALB. For GameServer or VoIP — NLB. We often combine them: ALB for web, NLB for WebSocket.

How ALB Works with Auto Scaling?

Attach an ALB target group to an Auto Scaling Group. When scaling, new instances automatically register and start receiving traffic. ALB health check (path /health, threshold of 2 successful responses) determines when the instance is ready to accept requests. This ensures zero-downtime deployment. For critical services we use target groups with deregistration_delay of 30 seconds to allow in-flight requests to complete.

Step-by-Step ALB Setup via Terraform

1. Create an ALB with security groups and subnets.
2. Configure HTTPS listener with ACM certificate and HTTP redirect.
3. Define target groups with health check and stickiness.
4. Add listener rules for routing by paths, headers, or hosts.
5. Attach target group to your service (EC2, ECS, Lambda).
6. Enable access logs and monitoring.

Full configuration example below.

Application Load Balancer

ALB is the standard choice for web applications. Routes by path, host, HTTP headers, method, query string. Integrates with ECS, EKS, Lambda, Auto Scaling Groups. Below is a complete configuration with AWS ALB, routing, and ACM.

# Terraform: полная конфигурация ALB + routing + ACM

resource "aws_lb" "main" {
  name               = "myapp-alb"
  internal           = false
  load_balancer_type = "application"
  security_groups    = [aws_security_group.alb.id]
  subnets            = aws_subnet.public[*].id

  enable_deletion_protection       = true
  enable_cross_zone_load_balancing = true
  drop_invalid_header_fields       = true

  access_logs {
    bucket  = aws_s3_bucket.alb_logs.bucket
    prefix  = "alb"
    enabled = true
  }

  tags = { Name = "myapp-alb" }
}

# HTTPS Listener
resource "aws_lb_listener" "https" {
  load_balancer_arn = aws_lb.main.arn
  port              = 443
  protocol          = "HTTPS"
  ssl_policy        = "ELBSecurityPolicy-TLS13-1-2-2021-06"
  certificate_arn   = aws_acm_certificate.main.arn

  default_action {
    type             = "forward"
    target_group_arn = aws_lb_target_group.web.arn
  }
}

# HTTP → HTTPS redirect
resource "aws_lb_listener" "http" {
  load_balancer_arn = aws_lb.main.arn
  port              = 80
  protocol          = "HTTP"

  default_action {
    type = "redirect"
    redirect {
      port        = "443"
      protocol    = "HTTPS"
      status_code = "HTTP_301"
    }
  }
}

# Target Group для веб-приложения
resource "aws_lb_target_group" "web" {
  name        = "myapp-web-tg"
  port        = 8080
  protocol    = "HTTP"
  vpc_id      = aws_vpc.main.id
  target_type = "ip"  # для ECS Fargate

  health_check {
    enabled             = true
    path                = "/health"
    healthy_threshold   = 2
    unhealthy_threshold = 3
    timeout             = 5
    interval            = 10
    matcher             = "200"
  }

  deregistration_delay = 30

  stickiness {
    type            = "lb_cookie"
    cookie_duration = 86400
    enabled         = false
  }
}

# API Target Group
resource "aws_lb_target_group" "api" {
  name     = "myapp-api-tg"
  port     = 3000
  protocol = "HTTP"
  vpc_id   = aws_vpc.main.id

  health_check {
    path    = "/api/health"
    matcher = "200"
  }
}

# Правила маршрутизации
resource "aws_lb_listener_rule" "api" {
  listener_arn = aws_lb_listener.https.arn
  priority     = 10

  action {
    type             = "forward"
    target_group_arn = aws_lb_target_group.api.arn
  }

  condition {
    path_pattern {
      values = ["/api/*"]
    }
  }
}

# Маршрут по заголовку (версионирование API)
resource "aws_lb_listener_rule" "api_v2" {
  listener_arn = aws_lb_listener.https.arn
  priority     = 5

  action {
    type             = "forward"
    target_group_arn = aws_lb_target_group.api_v2.arn
  }

  condition {
    http_header {
      http_header_name = "X-API-Version"
      values           = ["2", "2.0"]
    }
  }
}

# Weighted forwarding для Canary deployments
resource "aws_lb_listener_rule" "canary" {
  listener_arn = aws_lb_listener.https.arn
  priority     = 20

  action {
    type = "forward"
    forward {
      target_group {
        arn    = aws_lb_target_group.web_stable.arn
        weight = 95
      }
      target_group {
        arn    = aws_lb_target_group.web_canary.arn
        weight = 5
      }
      stickiness {
        enabled  = true
        duration = 3600
      }
    }
  }

  condition {
    path_pattern { values = ["/*"] }
  }
}

# Сертификат ACM
resource "aws_acm_certificate" "main" {
  domain_name               = "example.com"
  subject_alternative_names = ["*.example.com"]
  validation_method         = "DNS"

  lifecycle {
    create_before_destroy = true
  }
}

resource "aws_route53_record" "cert_validation" {
  for_each = {
    for dvo in aws_acm_certificate.main.domain_validation_options : dvo.domain_name => {
      name   = dvo.resource_record_name
      record = dvo.resource_record_value
      type   = dvo.resource_record_type
    }
  }

  zone_id = aws_route53_zone.main.zone_id
  name    = each.value.name
  type    = each.value.type
  ttl     = 60
  records = [each.value.record]
}

resource "aws_acm_certificate_validation" "main" {
  certificate_arn         = aws_acm_certificate.main.arn
  validation_record_fqdns = [for record in aws_route53_record.cert_validation : record.fqdn]
}

ALB + WAF

We integrate WAF for protection against OWASP top-10 and rate limiting.

resource "aws_wafv2_web_acl_association" "alb" {
  resource_arn = aws_lb.main.arn
  web_acl_arn  = aws_wafv2_web_acl.main.arn
}

resource "aws_wafv2_web_acl" "main" {
  name  = "myapp-waf"
  scope = "REGIONAL"

  default_action { allow {} }

  rule {
    name     = "AWSManagedRulesCommonRuleSet"
    priority = 1
    override_action { none {} }

    statement {
      managed_rule_group_statement {
        name        = "AWSManagedRulesCommonRuleSet"
        vendor_name = "AWS"
      }
    }

    visibility_config {
      cloudwatch_metrics_enabled = true
      metric_name                = "CommonRuleSet"
      sampled_requests_enabled   = true
    }
  }

  rule {
    name     = "RateLimit"
    priority = 2
    action { block {} }

    statement {
      rate_based_statement {
        limit              = 2000
        aggregate_key_type = "IP"
      }
    }

    visibility_config {
      cloudwatch_metrics_enabled = true
      metric_name                = "RateLimit"
      sampled_requests_enabled   = true
    }
  }

  visibility_config {
    cloudwatch_metrics_enabled = true
    metric_name                = "MyAppWAF"
    sampled_requests_enabled   = true
  }
}

ALB + ECS Fargate

Example of ALB integration with Fargate: the service automatically registers in the target group.

resource "aws_ecs_service" "app" {
  name            = "myapp-web"
  cluster         = aws_ecs_cluster.main.id
  task_definition = aws_ecs_task_definition.app.arn
  desired_count   = 3
  launch_type     = "FARGATE"

  network_configuration {
    subnets          = aws_subnet.private[*].id
    security_groups  = [aws_security_group.app.id]
    assign_public_ip = false
  }

  load_balancer {
    target_group_arn = aws_lb_target_group.web.arn
    container_name   = "web"
    container_port   = 8080
  }

  deployment_circuit_breaker {
    enable   = true
    rollback = true
  }

  deployment_controller {
    type = "ECS"
  }

  depends_on = [aws_lb_listener.https]
}

Network Load Balancer

NLB for TCP/UDP with static IPs and minimal latency.

resource "aws_lb" "nlb" {
  name               = "myapp-nlb"
  internal           = false
  load_balancer_type = "network"
  subnets            = aws_subnet.public[*].id

  enable_cross_zone_load_balancing = true
}

resource "aws_lb_listener" "nlb_tls" {
  load_balancer_arn = aws_lb.nlb.arn
  port              = 443
  protocol          = "TLS"
  ssl_policy        = "ELBSecurityPolicy-TLS13-1-2-2021-06"
  certificate_arn   = aws_acm_certificate.main.arn

  default_action {
    type             = "forward"
    target_group_arn = aws_lb_target_group.nlb_tcp.arn
  }
}

resource "aws_lb_target_group" "nlb_tcp" {
  name     = "myapp-nlb-tg"
  port     = 8080
  protocol = "TCP"
  vpc_id   = aws_vpc.main.id

  health_check {
    protocol            = "HTTP"
    path                = "/health"
    healthy_threshold   = 2
    unhealthy_threshold = 2
    interval            = 10
  }
}

Monitoring ALB

Key CloudWatch metrics: RequestCount, ActiveConnectionCount, TargetResponseTime (p50/p95/p99), HTTPCode_ELB_5XX_Count, HealthyHostCount, UnHealthyHostCount. We set up alerts for 5xx and high latency.

resource "aws_cloudwatch_metric_alarm" "target_5xx" {
  alarm_name          = "alb-5xx-errors"
  comparison_operator = "GreaterThanThreshold"
  evaluation_periods  = 2
  metric_name         = "HTTPCode_Target_5XX_Count"
  namespace           = "AWS/ApplicationELB"
  period              = 60
  statistic           = "Sum"
  threshold           = 10
  alarm_actions       = [aws_sns_topic.alerts.arn]

  dimensions = {
    LoadBalancer = aws_lb.main.arn_suffix
  }
}

resource "aws_cloudwatch_metric_alarm" "latency" {
  alarm_name          = "alb-high-latency"
  comparison_operator = "GreaterThanThreshold"
  evaluation_periods  = 3
  metric_name         = "TargetResponseTime"
  namespace           = "AWS/ApplicationELB"
  period              = 60
  extended_statistic  = "p95"
  threshold           = 2.0
  alarm_actions       = [aws_sns_topic.alerts.arn]

  dimensions = {
    LoadBalancer = aws_lb.main.arn_suffix
  }
}

What's Included in the Work

• Load balancing design: type selection (ALB/NLB), network scheme.
• Terraform code with target groups, listener rules, ACM, WAF.
• Monitoring and alert setup.
• Integration with CI/CD and Auto Scaling.
• Operations documentation and team training.

Implementation Timelines

Typical Configuration Mistakes

• Health check not configured — instances receive traffic before readiness.
• Deletion protection missing — accidental ALB deletion.
• Incorrect SSL policy — vulnerabilities.
• Click-through on WAF — managed rules not enabled.

We guarantee stability and performance. Get a consultation on ALB setup for your project. Contact us — we'll estimate timelines for your case. AWS ALB Documentation can help delve deeper into capabilities.

We regularly encounter a situation: "The site is not opening" at 3 a.m. — and it turns out that the VPS disk is full because nginx logs haven't been rotated for six months. Or the server went down under load on the day of an advertising campaign launch because the shared hosting had a limit of 50 concurrent connections. Setting up hosting and deployment is not about "where it's cheaper" but about what happens when something goes wrong. Our team helps avoid such incidents by designing infrastructure that accounts for real load patterns.

When to choose Vercel and Netlify?

Vercel is built for Next.js — deploy in one push, preview deployments for every PR, automatic CDN, Edge Functions, ISR without configuration. For frontend projects and JAMstack, it's the optimal choice: no operational overhead, time-to-deploy measured in minutes.

Real limitations: Vercel Serverless Functions run in us-east-1 by default (latency for Europe +80–100ms), Function timeout 300 seconds on Pro, Bandwidth 1TB/month on Pro. For heavy backend, you need workers or a separate server.

Netlify is closer to static sites and Edge Functions based on Deno Deploy. Build minutes are the main limitation on the free tier.

Why is Docker the foundation of predictable deployment?

"It works on my machine" — classic. Docker solves this through environment containerization. But a bad Dockerfile creates new problems.

A typical mistake: copying everything into the image without .dockerignore, resulting in an 800MB image instead of 80MB. node_modules inside the image weighs as much. Correct approach: multi-stage build.

FROM node:20-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci --only=production
COPY . .
RUN npm run build

FROM node:20-alpine AS runner
WORKDIR /app
COPY --from=builder /app/.next ./.next
COPY --from=builder /app/node_modules ./node_modules
COPY --from=builder /app/package.json ./package.json
EXPOSE 3000
CMD ["npm", "start"]

Final image: 180MB instead of 1.2GB. CI build time is reduced due to layer caching — if package.json hasn't changed, the layer with npm ci is taken from cache.

Docker Compose for local development and simple production scenarios: application + PostgreSQL + Redis in one configuration. For production on a single server, it's a perfectly viable option if there's no requirement for horizontal scaling.

More about containerization — Wikipedia: Docker.

How to set up Nginx as a reverse proxy?

Nginx in front of the application is standard for VPS and dedicated servers. Main functions: SSL termination, gzip, static files, rate limiting, upstream load balancing.

A configuration often done incorrectly: worker_processes auto — number of processes equals CPU count. worker_connections 1024 — that's 1024 per worker process. With 4 CPUs and 1024 connections = 4096 concurrent connections. For a high-traffic site, you need worker_connections 4096 and set keepalive_timeout 65.

For static assets with hash in the filename:

location ~* \.(js|css|woff2|png|webp)$ {
    expires 1y;
    add_header Cache-Control "public, immutable";
}

immutable tells the browser: don't revalidate this file even on hard refresh. This only works correctly with content-hashed filenames (which Vite/webpack do by default). Documentation — Wikipedia: Nginx.

AWS: flexibility and complexity

EC2 + Auto Scaling Group — classic for horizontal scaling. AMI with pre-installed application, Launch Template, ASG with min/desired/max instances, Application Load Balancer. When CPU > 70% for 3 minutes — scale out, when CPU < 30% for 15 minutes — scale in. Health check via ALB removes unhealthy instances from rotation.

ECS Fargate — containers without managing EC2. Deploy a Docker image, specify CPU/memory (512 CPU units = 0.5 vCPU, from 512MB memory), Fargate launches it. More expensive than Lambda, but no cold start and no timeout limitations. Suitable for long-running processes, WebSocket servers, heavy workers.

RDS for PostgreSQL with Multi-AZ: automatic failover in 1–2 minutes when primary fails. Read Replicas for scaling reads. RDS Proxy for connection pooling — Lambda functions cannot hold long-term connections, the proxy buffers this.

Kubernetes: when it is justified

K8s adds significant operational complexity. Justified when: multiple teams deploy independent services, fine-grained resource allocation per service is needed, canary deployments and blue/green without downtime are required.

AWS EKS, GKE, or managed k8s from Hetzner (cheaper). Helm charts for standard services. Horizontal Pod Autoscaler based on CPU and custom metrics (RPS via Prometheus).

For most startups and medium-sized projects, Kubernetes is overkill. ECS or Fly.io provide 80% of the capabilities with 20% of the operational complexity.

Monitoring and alerting

A server without monitoring is waiting for an incident. Minimal stack: Prometheus + Grafana (or Grafana Cloud for managed), alerting on disk > 80%, memory > 85%, CPU > 90% over 5 minutes, error rate > 1%. Uptime via Better Uptime or Upptime (self-hosted).

Logs: Loki + Grafana or CloudWatch Logs Insights. Structured JSON logs (winston, pino) are mandatory — otherwise, log searching becomes a pain.

What is included in hosting setup

• Audit of current infrastructure and load profiling
• Selection of target architecture (VPS, AWS, serverless, Kubernetes)
• Setting up CI/CD pipeline (GitHub Actions, GitLab CI) with automatic deployment
• IaC via Terraform or Pulumi (infrastructure as code)
• Configuration of Nginx, SSL certificates, HTTP/2, brotli
• Monitoring and alerting (Prometheus + Grafana, PagerDuty)
• Documentation of runbooks and team training

Additionally, contact us if you need migration from current hosting or integration with external services.

Work process

1. Audit of current infrastructure (2–5 days)
2. Selection of target architecture with load and budget justification (1–3 days)
3. Setting up CI/CD pipeline (GitHub Actions, GitLab CI) (2–5 days)
4. IaC via Terraform or Pulumi (3–10 days)
5. Setting up monitoring and alerting (2–5 days)
6. Documentation of runbooks and team training (1–3 days)

Our experience — 7 years on the market, over 50 projects, guarantee of operability after deployment.

Timeline

• Basic deployment on VPS with Docker + Nginx + CI/CD: 1–2 weeks.
• Setting up AWS infrastructure with Auto Scaling, RDS, CDN: 3–6 weeks.
• Migration to EKS from scratch: 6–12 weeks.
• Setting up Vercel/Netlify for JAMstack: 3–5 days.

The cost is calculated individually depending on complexity and scope of work. Get a consultation — we'll evaluate your architecture in one day.