Troubleshooting Guide: My Website or App is Slow Print

Performance Diagnosis Flowchart

Identify and fix performance issues with your ASP.NET Core application on Plesk Windows hosting.

Step 1: Where is the Slowness?

Section A: Cold Start / Initial Load Slow

Causes & Solutions:

1. Application Pool idle timeout
   • Default: 20 minutes idle = app unloads
   • Fix: Increase idle timeout in Plesk → Dedicated IIS Application Pool
2. Large application / many dependencies
   • Fix: Consider ReadyToRun compilation:

     <PublishReadyToRun>true</PublishReadyToRun>

3. JIT compilation on first request
   • Fix: Use warmup scripts or Application Initialization

Section B: General Slow Performance

Check These Items:

1. Enable compression

   builder.Services.AddResponseCompression();

2. Enable caching

   builder.Services.AddResponseCaching();
   builder.Services.AddOutputCache();

3. Minify CSS/JS - Use bundling in production
4. Optimize images - Use WebP format, lazy loading
5. Check for synchronous I/O
   • Use async/await for all I/O operations
6. Review logging level
   • Set to Warning or Error in production

Section C: Database Performance

Diagnostic Steps:

1. N+1 Query Problem
   • Symptom: Many small queries instead of one
   • Fix: Use Include() for eager loading:

     _context.Orders.Include(o => o.Items).ToListAsync()

2. Missing indexes
   • Fix: Add indexes to frequently queried columns
3. Large result sets
   • Fix: Implement pagination

     .Skip(page * size).Take(size)

4. Connection pooling issues
   • Ensure DbContext is scoped (not singleton)

Section D: Intermittent Slowness

Possible Causes:

1. Application Pool recycling
   • Check: Plesk → Application Pool settings
   • Review Private Memory Limit and recycling schedule
2. Memory pressure
   • Symptom: Slow after running a while
   • Fix: Check for memory leaks, increase memory limit
3. Garbage collection
   • Large object allocations cause GC pauses
   • Fix: Use ArrayPool, reduce allocations

Quick Wins Checklist

• ☐ Enable Response Compression
• ☐ Enable Output Caching
• ☐ Set logging to Warning level
• ☐ Use async/await everywhere
• ☐ Bundle and minify static files
• ☐ Add database indexes
• ☐ Implement pagination
• ☐ Review Application Pool memory limits