Discover and fix application hangs the right way

Struggling with IIS and .NET performance issues? Diagnose them correctly with a lightweight diagnostic service that really gets your applications.

Built and backed by engineers that created the Microsoft web platform.


Severe hang in the MvcApp application pool with 86 requests blocked for over 20s.

Determines root cause:

Hang caused by ASP.NET thread pool exhaustion due to ProfileHelper.GetProfile().

Understands IIS & .NET:

Diagnoses queueing, concurrency limits, threading issues, garbage collection, and dozens of other platform issues. Learn more →


Crash caused abnormal termination in the MvcApp application pool.

Determines root cause:

Crash caused by Stack overflow in ProfileHelper.ScavengeProfileCache().

Automatically diagnoses hard-to-catch crashes:

Stack overflow, unhandled exceptions, worker process timeouts. Learn more →

High CPU

Cpu overload caused by the MvcApp application pool.

Determines root cause:

Cpu overload caused by hot path in ProfileHelper.GetPurchases().

Optimize the right places:

Automatically identifies hot paths in your application code that cause trouble. Learn more →

Memory leaks

Memory leak detected in the MvcApp application pool.

Determines root cause:

Large byte[] arrays caused memory leak on the Large Object Heap.

Finally solve memory issues the right way:

Stop recycling, and optimize the exact code responsible for memory leaks and excessive garbage collection. Learn more →

find and fix:

  • Slow requests
  • Lock contention
  • Errors
  • Classic ASP
  • Recycling
  • and more ...

Used by 10,000+ companies to solve real performance issues.

Dan O'Connell

Senior Developer, Millstone Medical
This is a fantastic product. We were able to improve speed noticeably on a horrow-show of a server. Seriously, this is really good stuff... you're going to make a hero out of me.

Safer & lower overhead

external non-blocking APM side-by-side
Lightweight, non-intrusive monitoring

LeanSentry uses external, low-overhead monitoring based on IIS log files, performance counters, WMI, and ETW tracing.

Unlike an APM tool, we do not attach any profilers or inject agents into your process that can crash or slow down your apps.

Automatic diagnostics

LeanSentry automatically detects hangs, high CPU usage, or memory leaks - and performs deeper diagnostics to get you code-level details.

These diagnostics typically last seconds, and give you the details you need at the right time.

24/7 coverage
HTTPS no memory
Safe and secure

LeanSentry collects non-sensitive data that is considered safe to log to standard Windows logs. It does not access your application's memory, data, and code.

Locked down environment? Use LeanSentry OnPremise to host your own data with no outside communication.

About Us
Mike Volodarsky founded LeanSentry after working on the IIS 7.0 and ASP.NET 2.0 products at Microsoft.

LeanSentry is based on tools and techniques developed while working with some of the largest Microsoft-based websites in the world, including MySpace, Vevo, Microsoft mobile, and hundreds of others.

See what you've been missing.

See what really causes your performance issues
Diagnose slow requests and website hangs down to the code. LeanSentry understands concurrency limits, threading issues, and queueing and can find your application code that's causing it.
Find and fix errors across entire server stack
Track errors across your entire stack, including your server, IIS, ASP.NET, and your application. Give your developers the details they need to fix errors quickly.
Optimize .NET performance
Tune memory usage

Troubleshooting memory leaks in production can be incredibly hard.

LeanSentry automatically tracks memory leaks, and helps you proactively tune your app's memory usage.

  • See exactly where memory was allocated.
  • Understand how .NET Garbage collection affects your performance.
  • Track .NET memory usage down to code.

Tune CPU usage

Troubleshoot high CPU usage, or reduce your app's CPU overhead to save your server costs.

  • Near-continuous CPU usage history down to application code.
  • Low overhead with no heavy profilers.

Track down performance regressions and validate improvements, without doing extensive performance testing.

You are going to like this.

Deploy in 5 minutes. No iisreset. Runs safely alongside other APMs.
Upgrade your toolset
For Operations
For Teams
Application Health
Quickly track health and performance.
Request Debugger
Get full request traces for errors and slow requests. Log custom data into the trace.
Reduce Testing Costs
Save time and get better results: let your developers tune performance in production.
Get notified on slow pages, errors, low memory, high CPU, and more.
Identify Slow Code
Identify slow functions blocking requests, down to line of code.
Boost App Performance
Expert insight makes it easier for your team to improve and maintain high performance.
Get the Evidence
Is the server or the code? We'll tell you. Simply link your teammates to the evidence.
Go Straight to Fixing
Get the full info on issues: stack traces, CPU trees, memory graphs. No guessing, setting up repros, and production debugging.
Slash Server Costs
Because tuning CPU and memory is so easy, you can reduce your footprint and run it with fewer servers in no time.

Get started!

Deploy LeanSentry to your servers, and view diagnostics in minutes on our online dashboard.
Deploy and start diagnosing in 5 minutes.
Host the entire LeanSentry stack in your environment.
Our customers say