A client recently contacted me after their WooCommerce store on SiteGround Cloud started autoscaling from 14 CPU cores to nearly 40 cores within just a few days. RAM usage was climbing, 503 errors were appearing, and the WordPress backend had become painfully slow. In this case study, I’ll walk you through how I diagnosed the real cause — and what we did to stabilize the server.
Table of Contents
The website was a high-traffic WooCommerce store (50k+ daily visitors) running on SiteGround Cloud Hosting.
Let me walk you through how we investigated it — and what actually fixed it.
Step 1 – Verify It’s Not a Hosting Glitch
First, I checked the resource graphs inside SiteGround.
What we saw:
CPU spikes reaching 20–30 cores
Frequent 503 (Service Unavailable) errors
499 client timeout errors
RAM relatively stable
This told me something important:
👉 The load was real.
👉 This wasn’t a hosting bug.
👉 Something was generating heavy concurrent PHP execution.
Step 2 – Identify Abnormal Request Patterns
Next, I checked:
Most visited pages
AJAX endpoints
Error distribution
That’s where we found the first major problem:
/wp-admin/admin-ajax.php→ 200,000+ hitsA plugin endpoint generating massive traffic
The culprit?
A WordPress analytics plugin aggressively calling AJAX on every visit.
Action Taken:
I disabled the plugin.
Result:
CPU usage immediately dropped.
Step 3 – Why CPU Was Still High After That
Even after removing the high-AJAX plugin, CPU was still fluctuating.
So we inspected response headers.
We found:
x-proxy-cache: MISS
SKIP_CACHE_SET_COOKIE
WooCommerce was setting session cookies on product pages.
That means:
Product pages were NOT being cached
Every visitor triggered full PHP execution
At 50k daily visitors → that’s heavy load
Even with:
SiteGround CDN
Dynamic Cache enabled
Memcached enabled
WooCommerce sessions force cache bypass.
This is a structural limitation.
Step 4 – Heavy Plugin Stack
The site had:
40+ active plugins
Multiple discount engines
Currency switcher
Product filter system
Rewards system
Elementor + Woodmart
Multiple analytics integrations
Each product page load was running:
Pricing calculations
Currency conversion
Filter queries
Tracking scripts
Under high traffic, this stacks up.
Step 5 – PHP Version Problem
The site was running PHP 8.0 (end-of-life).
I attempted upgrading to PHP 8.2 for performance gains.
Result:
502 Bad Gateway.
This confirmed:
👉 Some plugins/theme components were outdated and incompatible.
Fixing that requires:
Staging environment
Compatibility testing
Controlled upgrades
That’s a separate modernization project.
What We Fixed
✔ Disabled high-load AJAX plugin
✔ Verified caching configuration
✔ Reduced backend load by disabling Jetpack
✔ Confirmed scheduled tasks weren’t retrying
✔ Stabilized autoscaling behavior
After changes, CPU usage reduced significantly — spikes normalized.
Why SiteGround Was Limiting Further Optimization
Here’s the important part.
SiteGround Cloud:
Does not allow Redis object caching
Does not allow deep PHP-FPM tuning
Restricts server-level optimization
Controls caching rules (limited flexibility)
For high-traffic WooCommerce stores, you eventually hit architectural limits.
You can’t fully optimize dynamic workloads without:
Redis
Proper PHP worker tuning
Full NGINX stack control
Custom caching strategy
That’s simply not possible inside managed shared/cloud panels like SiteGround.
The Real Long-Term Solution
For this level of traffic, the correct architecture would be:
Properly configured VPS
Redis object caching
Tuned PHP-FPM workers
Optimized database
Edge caching with controlled bypass rules
Modern PHP version (8.2+ or newer)
Estimated cost for a suitable VPS setup: ~$250–$300/month.
But performance becomes predictable. No surprise autoscaling.
My Managed VPS Approach
For clients running serious WooCommerce operations, I offer fully managed VPS environments designed specifically for performance and stability.
This includes:
Server provisioning & hardening
Performance-tuned NGINX + PHP-FPM stack
Redis object caching
Proper WooCommerce cache bypass configuration
Continuous monitoring
No hidden autoscaling surprises
Instead of paying unpredictable cloud scaling fees, you get controlled, optimized infrastructure built for growth.
For a store at this scale, a properly configured VPS typically starts around $250–$300/month, but delivers significantly more control, stability, and performance.
Key Takeaways
If you are experiencing:
CPU autoscaling on SiteGround
503 / 499 errors
WooCommerce backend slowness
Product pages not caching
High admin latency
PHP upgrade crashes
You likely have:
Heavy dynamic plugin stack
Session-based cache bypass
Hosting architecture limitations
Outdated PHP compatibility
Final Thoughts
This case was not a “server issue.”
It was an architectural and plugin-load issue.
We solved the immediate autoscaling crisis.
But long-term scalability requires deeper infrastructure changes.
Need Help?
If your WooCommerce store:
Keeps autoscaling
Runs slow under traffic
Shows 502/503 errors
Or backend is unusable
I can help diagnose the real root cause and design a proper optimization plan.