1. Introduction

As your WordPress website grows, handling increased traffic efficiently becomes crucial. Horizontal scaling involves adding more servers to distribute the load, enhancing performance, and ensuring high availability. AWS provides robust tools like Elastic Load Balancing, Auto Scaling Groups, and shared storage solutions to facilitate this process.

2. Prerequisites

• AWS Account: An active AWS account with administrative privileges.
• Basic AWS Knowledge: Familiarity with services like EC2, RDS, EFS, ELB, and networking concepts.
• WordPress Experience: Understanding of installing and configuring WordPress.
• Domain Name: A registered domain for your WordPress site.
• AWS CLI (Optional): Installed and configured for advanced operations.

3. Understanding Horizontal Scaling

Horizontal scaling (scaling out) involves adding more machines to your pool of resources. This is in contrast to vertical scaling (scaling up), which increases power on existing machines. Key benefits include improved performance, high availability, and flexibility.

4. AWS Services Overview

The following AWS services will be used:

• Amazon EC2: Virtual servers for WordPress instances.
• Amazon RDS: Managed relational database.
• Amazon EFS: Shared file storage.
• Amazon ELB: Distributes incoming traffic.
• Amazon Auto Scaling: Adjusts the number of EC2 instances.
• Amazon VPC: Virtual network for resources.
• Amazon ElastiCache: In-memory caching (Redis/Memcached).
• Amazon CloudFront: Content Delivery Network (CDN).
• Amazon Route 53: DNS management service.
• AWS Certificate Manager: Manages SSL/TLS certificates.

5. Architecture Overview

To horizontally scale WordPress on AWS, the architecture includes:

• Amazon EC2: Multiple servers running WordPress.
• Application Load Balancer (ALB): Distributes traffic across EC2 instances.
• Amazon RDS: Centralized relational database.
• Amazon EFS: Shared file system for uploads and plugins.
• Auto Scaling Group (ASG): Adjusts number of EC2 instances based on demand.
• Amazon ElastiCache: Improves performance through caching.
• Amazon CloudFront: Speeds up content delivery.
• Amazon Route 53: Manages domain resolution.

6. Setting Up the Virtual Private Cloud (VPC)

Setting up a secure and efficient network is the foundation for scaling. Follow these steps to configure your VPC:

Steps:

1. Create a VPC with CIDR block (e.g., 10.0.0.0/16).
2. Create Public and Private Subnets in different Availability Zones.
3. Set up an Internet Gateway for public subnet access.
4. Configure route tables for public and private traffic.
5. (Optional) Set up a NAT Gateway to allow private instances internet access.

7. Configuring the Database Layer with Amazon RDS

Using Amazon RDS as your managed database service ensures data consistency and reliability. Follow these steps:

Step 1: Launch an RDS Instance

• Choose MySQL or MariaDB as your engine.
• Configure instance settings like size, storage, and credentials.
• Select your VPC and private subnets for deployment.

Step 2: Configure Security Groups

• Edit security groups to allow MySQL connections from EC2 instances.
• Ensure your EC2 security group can access the RDS instance.

Step 3: Note the RDS Endpoint

After the RDS instance is available, note the endpoint URL for configuring WordPress.

8. Setting Up Shared File Storage with Amazon EFS

Amazon EFS allows EC2 instances to share the wp-content/uploads directory. Follow these steps:

Step 1: Create an EFS File System

• Create an EFS file system in your VPC.
• Add mount targets in each Availability Zone where EC2 instances reside.
• Set permissions to allow NFS traffic from EC2 instances.

Step 2: Mount EFS on EC2 Instances

• Install NFS utilities on your EC2 instances.
• Mount the EFS file system to /var/www/html/wp-content/uploads.
• Ensure the mount persists by editing /etc/fstab.

9. Creating a Custom AMI for WordPress Instances

Create a custom AMI to ensure consistency across EC2 instances in your Auto Scaling Group.

Step 1: Launch a New EC2 Instance

• Choose the latest Amazon Linux 2 or Ubuntu Server LTS AMI.
• Select an instance type (e.g., t3.medium).
• Place the instance in private subnets and assign necessary security groups.

Step 2: Install Required Software

• Install Apache, PHP, and WordPress on the EC2 instance.
• Set up permissions and mount EFS for media uploads.

Step 3: Create a Custom AMI

• Clean up sensitive data, and create an image from the instance via EC2 Console.

10. Setting Up Auto Scaling Groups

Auto Scaling Groups (ASG) automatically adjust the number of EC2 instances based on demand.

Step 1: Create a Launch Template

• Create a launch template with your custom AMI, instance type, and network settings.
• Optionally, add user data scripts to mount EFS and start services on boot.

Step 2: Create an Auto Scaling Group

• Attach the launch template and set desired capacity (e.g., 2 instances).
• Attach the Auto Scaling Group to your Application Load Balancer.

11. Configuring the Application Load Balancer

An Application Load Balancer (ALB) distributes incoming traffic across multiple EC2 instances, ensuring no single instance is overwhelmed.

Step 1: Create an Application Load Balancer

• Create an ALB and configure HTTP and HTTPS listeners.
• Associate the ALB with your public subnets and security groups.

Step 2: Configure Target Group

• Create a target group for your EC2 instances and configure health checks.
• Ensure your Auto Scaling Group registers instances automatically with the ALB.

12. Configuring Security Groups

Security groups ensure that your AWS resources communicate securely.

EC2 Instances:

• Allow HTTP (port 80) and NFS (port 2049) traffic from the relevant security groups.

Load Balancer:

• Allow HTTP (port 80) and HTTPS (port 443) traffic from the internet.

RDS:

• Allow MySQL traffic from EC2 instances on port 3306.

EFS:

• Allow NFS traffic from EC2 instances on port 2049.

13. Setting Up WordPress

With the infrastructure in place, configure WordPress:

• Edit wp-config.php to connect to your RDS database.
• Set up object caching with ElastiCache (optional).
• Ensure uploads are stored on EFS or use Amazon S3 for media storage.

14. Domain and SSL Configuration

Configure your domain and set up SSL certificates:

Step 1: Obtain an SSL Certificate

• Request an SSL certificate from AWS Certificate Manager (ACM).
• Validate the certificate by adding a DNS record to your domain registrar.

Step 2: Attach Certificate to Load Balancer

• Edit the HTTPS listener on your ALB to use the certificate from ACM.

Step 3: Update DNS Records

• Point your domain’s DNS records to the ALB or CloudFront distribution.

15. Testing and Validation

Ensure all components work together seamlessly:

• Access your website via the domain and verify SSL.
• Simulate traffic and verify load balancing and Auto Scaling functionality.
• Test media uploads to ensure they persist across instances via EFS or S3.

16. Optimizing with Amazon ElastiCache

Caching improves performance by reducing load on your database:

• Launch an ElastiCache cluster with Redis or Memcached.
• Install the appropriate PHP modules (e.g., php-redis) on EC2 instances.
• Configure WordPress to use caching for faster load times.

17. Implementing Amazon CloudFront CDN

Use CloudFront to speed up content delivery globally:

• Create a CloudFront distribution and set the origin domain to your ALB.
• Configure SSL/TLS with your ACM certificate for secure content delivery.
• Point your DNS records to the CloudFront distribution for global performance.

18. Monitoring and Logging

Monitor your infrastructure to ensure it performs efficiently:

• Set up CloudWatch alarms for CPU, memory, and network metrics.
• Enable access logging for ALB, CloudFront, and RDS.
• Use AWS CloudWatch Logs to centralize logs from EC2 instances.

19. Additional Considerations

Backup Strategy:

• Enable automatic backups for RDS and EFS.
• Consider EFS-to-EFS backups for data redundancy.

Disaster Recovery:

• Consider multi-region deployments for improved resilience.

Cost Optimization:

• Use Reserved Instances for long-term use or Spot Instances for cost savings.

20. Conclusion

By following this comprehensive guide, you have successfully set up a horizontally scalable WordPress architecture on AWS. This setup leverages AWS services to distribute load, manage stateful data, and ensure your WordPress site remains performant and resilient. Next Steps:

• Regularly perform security audits to ensure compliance with best practices.
• Continuously monitor and optimize performance.
• Keep your WordPress installation and plugins updated.