Best Application Monitoring Tools
See inside your applications before users tell you something's broken
TL;DR
Datadog is the modern observability leader with best-in-class UX and broad coverage. New Relic offers strong APM with generous free tier for cost-conscious teams. Sentry is essential for error tracking regardless of other tools. For infrastructure-heavy workloads, consider Prometheus + Grafana as an open-source option.
Modern applications are complex distributed systems. When something goes wrong, you need more than server metrics—you need to trace requests across services, understand application behavior, and catch errors before users complain. The observability market has consolidated around a few major platforms, but costs can spiral quickly. Here's how to get visibility without overspending.
What is Application Monitoring?
Application monitoring (APM) provides visibility into how your applications perform—response times, error rates, throughput, and traces through distributed systems. Modern observability extends this with infrastructure metrics, log aggregation, and real user monitoring. The goal: understand application health and quickly identify issues when things go wrong.
Why Application Monitoring Matters
You can't fix what you can't see. Without monitoring, you discover problems from user complaints—the worst way to learn. Good APM catches issues early, helps you understand performance trends, and dramatically reduces time to resolution. For production systems, it's not optional—it's insurance that pays for itself with every incident avoided.
Key Features to Look For
Distributed Tracing
essentialFollow requests across microservices to identify bottlenecks
Error Tracking
essentialCapture, aggregate, and alert on application errors with context
Metrics & Dashboards
essentialVisualize application and infrastructure health
Alerting
essentialGet notified when things go wrong, with smart noise reduction
Log Management
importantCentralize and search application logs
Real User Monitoring
importantSee actual user experience in browsers and apps
Infrastructure Monitoring
importantTrack servers, containers, cloud resources
AI/ML Analysis
nice-to-haveAnomaly detection and intelligent alerting
Key Factors to Consider
- What do you need to monitor? APM vs. infrastructure vs. logs—scope matters for cost
- Language and framework support—ensure your stack is well-covered
- Pricing model: per-host, per-GB, per-trace—understand what drives your bill
- Data retention needs—logs and traces are expensive to store long-term
- Integration with your deployment and incident management tools
Pricing Overview
APM pricing is complex—based on hosts, data volume, features. Costs can escalate quickly at scale.
Free/Starter
$0-$25/host/month
Small applications, limited features
Professional
$25-$75/host/month
Growing applications, full APM features
Enterprise
$75-$200+/host/month
Large scale, advanced features, premium support
Top Picks
Based on features, user feedback, and value for money.
Datadog
Top PickThe modern observability platform leader
Best for: Teams wanting comprehensive observability with excellent UX
Pros
- Excellent user experience
- Comprehensive platform
- Great integrations
- Strong community
Cons
- Expensive at scale
- Complex pricing
- Can be overwhelming
- Vendor lock-in concerns
New Relic
Full-stack observability with generous free tier
Best for: Teams wanting strong APM with cost-effective entry point
Pros
- 100GB free forever
- Strong APM heritage
- Good all-in-one platform
- Simpler pricing model
Cons
- Interface less polished than Datadog
- Some features feel dated
- Free tier has limits
- Can be complex
Sentry
Essential error tracking for every development team
Best for: Any team that wants to catch and fix errors before users notice
Pros
- Best-in-class error tracking
- Excellent developer experience
- Good free tier
- Easy to integrate
Cons
- Focused on errors, not full APM
- Performance monitoring newer
- Pricing can surprise
- Less infrastructure focus
Common Mistakes to Avoid
- Sending all logs to APM tools when you don't need them—cost explodes
- Not setting up alerting properly—monitoring without alerts is just dashboards
- Paying for full platform when you only need error tracking
- Ignoring open-source options like Prometheus for infrastructure metrics
- Over-instrumenting and creating performance overhead
Expert Tips
- Start with Sentry for errors—it's essential and focused
- Sample traces in production, don't capture everything—costs add up
- Set meaningful alerts, not everything—alert fatigue kills effectiveness
- Consider splitting: Sentry for errors, Prometheus for metrics, specific APM for traces
- Monitor your monitoring costs—set budgets and alerts on spend
The Bottom Line
Use Sentry for error tracking—it's excellent and affordable. For full APM, Datadog offers the best experience if budget allows. New Relic's free tier is generous for getting started. At scale, consider Prometheus + Grafana for infrastructure metrics to control costs. The goal is visibility, not checking vendor boxes.
Frequently Asked Questions
Do I need both APM and error tracking?
APM includes basic error tracking, but dedicated error trackers like Sentry provide much better error management—grouping, assignment, release tracking. Many teams use both: APM for performance visibility, Sentry for error workflows.
How much does application monitoring really cost?
It varies wildly—from free tiers to hundreds of thousands per year at scale. Key cost drivers: number of hosts, data volume (especially logs), retention period, and features enabled. Start small and understand your usage patterns.
Should I use open-source monitoring tools?
Prometheus + Grafana is excellent for metrics and dashboards, especially at scale. But operational overhead is real—you're running the monitoring infrastructure. Managed services cost more but let you focus on your product.
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