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Synthetic Monitoring – Complete Guide

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1. Observability Foundation

Modern observability is not a single tool, but a stack of complementary signals:

Infrastructure + Logs + APM + Synthetic + RUM
============================================
                Alerts + Dashboards

Role of Each Signal

Layer	Purpose
Infrastructure Monitoring	CPU, memory, disk, network, nodes
Log Monitoring	Errors, warnings, audit trails
APM	Traces, service latency, dependencies
Synthetic Monitoring	Proactive availability & performance checks
RUM (Real User Monitoring)	Actual end-user experience

👉 Synthetic Monitoring fills the proactive gap: it tells you something is broken before real users complain.

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2. What Is Synthetic Monitoring?

Synthetic Monitoring is a technique where automated scripts simulate user or system behavior by sending requests to your application at regular intervals.

These scripts:

• Call endpoints
• Validate availability
• Measure performance
• Check correctness

Even if no real users are active, synthetic monitoring still runs.

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3. Core Concept (From Your Notes)

SCRIPT  --->  ENDPOINT (API / HTTP / TCP / UDP)
                 |
              UP or DOWN?

Key Characteristics

• Script-driven
• Predictable execution
• Runs on schedule
• Independent of real traffic

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4. What Can Synthetic Monitoring Test?

Supported Protocols

Protocol	Use Case
HTTP / HTTPS	REST APIs, websites
API (REST / GraphQL)	Backend services
TCP	Database ports, SMTP, SSH
UDP	DNS, VoIP, streaming
ICMP	Basic reachability (ping)

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5. Types of Synthetic Monitoring

5.1 API / HTTP Synthetic Monitoring (No JavaScript)

Characteristics

• Direct HTTP calls
• JavaScript not executed
• Lightweight and fast
• Ideal for backend checks

Typical Checks

• Status code (200/201/etc.)
• Response time
• Response body validation
• Headers and auth
• TLS handshake

Example

Client (Synthetic Agent) ---> HTTP API
                              |
                          JSON Response
Code language: JavaScript (javascript)

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5.2 Browser Synthetic Monitoring (JavaScript Executed)

Characteristics

• Uses a real browser
• Executes JavaScript
• Simulates real user behavior
• Heavier than API checks

Typical Scenarios

• Login flow
• Form submission
• SPA loading (React / Angular / Vue)
• Checkout journey

Example

Synthetic Browser ---> Load HTML ---> Execute JS ---> DOM rendered

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6. Where Are Synthetic Scripts Hosted?

Script Hosting Model

=============================
SCRIPT hosted by Monitoring Platform
=============================

In tools like Dynatrace, scripts are:

• Centrally managed
• Versioned
• Secure
• Executed by managed agents

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7. Global Execution Locations (15+ Regions)

Scripts run from multiple geographic regions:

USA   ---> API ---> Latency / Availability
INDIA ---> API ---> Latency / Availability
EU    ---> API ---> Latency / Availability

Why Global Locations Matter

• Detect regional outages
• Measure geo-latency
• Validate CDN behavior
• Catch ISP-specific issues

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8. What Exactly Is Tested in a Synthetic Request?

From your notes:

https
  protocol
  load
  auth
    pass
    cert
    token
  body
  param

Detailed Breakdown

8.1 Protocol

• HTTP / HTTPS
• TLS version
• Cipher negotiation

8.2 Load & Performance

• DNS resolution time
• TCP connect time
• TLS handshake time
• Time to first byte (TTFB)
• Total response time

8.3 Authentication

Type	Example
Basic Auth	Username + Password
Token	Bearer / OAuth / JWT
Certificate	mTLS
Custom Headers	API keys

8.4 Request Body

• JSON
• XML
• Form data
• GraphQL payload

8.5 Parameters

• Query parameters
• Path variables
• Headers

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9. Availability vs Performance

Synthetic Monitoring checks both:

Aspect	Example
Availability	Endpoint reachable?
Performance	Response < 500ms?
Correctness	JSON field exists?
Security	TLS valid?

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10. Alerting & Dashboards

Alert Flow

Synthetic Failure
      ↓
Alert Rule Triggered
      ↓
Notification (Slack / Email / PagerDuty)

Dashboards Show

• Uptime %
• Response time trends
• Region-wise comparison
• Failure root causes

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11. Synthetic vs RUM (Critical Difference)

Synthetic Monitoring	RUM
Proactive	Reactive
Script-based	Real users
Controlled	Uncontrolled
Runs 24×7	Runs when users exist

👉 Best practice: Always use Synthetic + RUM together.

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12. Common Use Cases

• API health checks
• Login page monitoring
• SSL certificate expiry checks
• Geo-availability validation
• Pre-release testing
• SLA / SLO verification

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13. Best Practices

Design

• Keep scripts small and focused
• Separate API and browser checks
• Avoid unnecessary UI steps

Execution

• Run from multiple regions
• Use realistic authentication
• Set meaningful thresholds

Alerting

• Avoid alert storms
• Combine with APM context
• Alert on user-impacting failures

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14. Synthetic Monitoring in Observability Strategy

Infra + Logs + APM + Synthetic + RUM
===================================
        Single Pane of Glass

Synthetic Monitoring acts as:

• Early warning system
• External viewpoint
• SLA guardian

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15. Summary

Synthetic Monitoring:

• Uses scripts to test endpoints
• Works with HTTP, API, TCP, UDP
• Runs globally from managed regions
• Tests availability, performance, and correctness
• Complements APM and RUM
• Enables proactive incident detection