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CloudCost Buddy: Automating AWS Budget Auditing with a Cost Watch Agent

CloudCost Buddy: Automating AWS Budget Auditing with a Cost Watch Agent

Learn how CloudCost Buddy models AWS multi-service architectures and uses a goal-based software agent to proactively detect budget overruns and provide actionable rightsizing steps.

Building CloudCost Buddy: A Goal-Based Cost Watch Agent for AWS Cloud Architectures

A submission for the AWS Builder Weekend Challenge: Build an Agent

🚀 Live Demo & Links

💡 The Problem: The AWS Cloud Bill Blindspot

Estimating and governing cloud infrastructure costs is one of the most critical challenges developers and architects face. While AWS provides enterprise-grade calculators and AWS Cost Explorer, engineers often encounter several hurdles during early-stage prototyping and project planning:
  1. Complex calculators: Sifting through hundreds of parameters when you just want a quick, realistic baseline architecture estimate.
  2. Post-facto surprises: Finding out you breached a personal or startup project budget only after the monthly AWS bill arrives.
  3. Actionability gap: Knowing a dollar amount is useful, but knowing what technical trade-offs will reduce costs without breaking architecture requirements is much more valuable.
To tackle this problem for the AWS Builder Weekend Challenge, I built CloudCost Buddy — an intuitive, client-side AWS cost estimation platform paired with an intelligent Cost Watch Agent.

🤖 What is the Cost Watch Agent?

In the AI and software engineering world, an agent is defined as an entity that:
  1. Perceives its environment,
  2. Evaluates current state against a defined goal or boundary, and
  3. Acts or recommends actions to achieve that desired goal state.
While many challenge entries lean towards generative LLMs, generative models can introduce latency, non-deterministic hallucinations, recurring API token fees, and privacy concerns when analyzing sensitive cloud infrastructure blueprints.
For CloudCost Buddy, I built a Goal-Based Heuristic Software Agent that operates with 100% determinism, zero external API costs, and sub-millisecond execution directly in your browser.
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+-----------------------------------------------------------------+
| Cost Watch Agent Workflow |
+-----------------------------------------------------------------+
|
[1. Perceive: Inspect Saved Blueprints]
|
[2. Compute: Calculate Monthly Costs]
|
[3. Evaluate: Compare with Budget Goal ($)]
|
+----------------+----------------+
| |
[Within Budget] [Budget Breached]
| |
Status: Healthy Status: Alert
|
[4. Synthesize Findings]
|
[5. Generate Remediation Plan]
• Downsizing opportunities
• Tiering & lifecycles
• Concurrency optimizations

Agent Architecture: Perception to Action

  • Environment & State Perception: The agent continuously accesses and parses the active architectural estimates stored in local state/storage.
  • Goal Condition: A user-customizable monthly spending limit (e.g., $500/month).
  • Heuristic Auditing Engine: The agent recalculates baseline costs across all provisioned services (EC2, S3, Lambda, DynamoDB) using verified regional pricing structures (US East N. Virginia).
  • Goal-Directed Diagnostics: If an architecture exceeds the threshold, the agent isolates the exact culprit services contributing the highest proportion of the overrun.
  • Actionable Remediation Generation: The agent formulates concrete, step-by-step mitigation plans — recommending EC2 instance right-sizing, S3 Intelligent-Tiering, Lambda memory rightsizing, and DynamoDB capacity optimizations.

🖥️ Key Features of CloudCost Buddy

1. Modern AWS-Inspired Dark Dashboard

  • Executive Summary Cards: Instant visibility into Monthly Costs, Annual Projections, Active Services, and Top Cost Drivers.
  • Service Distribution Visualizations: Dynamic bar charts and category breakdowns rendered with smooth micro-interactions.
  • Global AWS Region Selector: Switch regions with context-aware pricing labels.

2. Multi-Service Cloud Cost Modeler

Configure realistic parameters across core AWS primitives:
  • Amazon EC2: Select instance types (t3.micro, t3.small, t3.medium, m5.large, etc.), running hours, and EBS volume allocation.
  • Amazon S3: Model Standard Storage, Infrequent Access (IA), Intelligent-Tiering, and expected data retrieval queries.
  • AWS Lambda: Configure request invocation volume, average execution duration (ms), and allocated memory (MB) with automatic Free Tier deductions.
  • Amazon DynamoDB: Balance read/write capacity units (RCU/WCU) alongside persistent indexed storage.

3. Architecture Blueprint Templates

Get started in one click with pre-engineered architectures:
  • Scalable Web Application: Balanced compute, object storage, and serverless background workers.
  • Serverless Microservice API: Pure API Gateway, Lambda, and DynamoDB architecture.
  • Data Lake & Processing Pipeline: Heavy S3 storage footprint with on-demand compute batch jobs.

4. Client-First Privacy & Portability

  • Zero Backend Footprint: No credentials or architecture diagrams ever leave your browser.
  • Persistent Local State: Automatic localStorage synchronization across reloads.
  • Export & Share: Export complete cost models and itemized breakdowns to formatted JSON or CSV for executive stakeholder reports.

🛠️ How It Was Built

CloudCost Buddy was engineered with modern frontend and cloud technologies:
  • React 18 & TypeScript: Strict type safety across all estimation equations, recommendation rule engines, and agent data contracts.
  • Vite: High-performance local development and optimized production bundling.
  • Recharts & Lucide React: Accessible, modern data visualizations and AWS-style iconography.
  • AWS Amplify Hosting: Continuous automated deployment connected to the Git repository, serving the application globally via Amazon CloudFront CDN edges with SSL.

🧪 Rigorous Testing & Reliability

A cost estimator and governance agent is only as good as its mathematical accuracy. CloudCost Buddy includes an automated unit testing suite powered by Vitest:
  • 11+ Unit Tests Passing:
    • Accurate monthly amortization of EC2 instance hours.
    • Multi-tier S3 gigabyte calculations and request fees.
    • Sub-cent precision for AWS Lambda execution compute-seconds.
    • Agent budget breach detection, threshold warnings, and remediation parsing logic.
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✓ src/features/calc/calculateCost.test.ts (6 tests)
✓ src/features/agent/costWatchAgent.test.ts (5 tests)

Test Files 2 passed (2)
Tests 11 passed (11)

🔮 Future Roadmap & AWS Integration

While CloudCost Buddy runs entirely client-side today for instant accessibility, the architecture is designed to expand seamlessly into native AWS cloud services:
  1. Amazon Bedrock Integration: Enhance the heuristic remediation engine with Claude 3.5 Sonnet / Amazon Titan to generate natural language infrastructure-as-code (Terraform/CloudFormation) refactoring scripts.
  2. AWS Pricing API Real-Time Sync: Replace static pricing tables with an AWS Lambda function querying the AWS Price List API.
  3. AWS EventBridge + SNS Alerts: Schedule headless agent audits that dispatch budget alerts directly to Slack or email.

🎯 Conclusion

The AWS Builder Weekend Challenge is all about shipping practical, inventive solutions that empower builders. With CloudCost Buddy, developers gain immediate clarity over their AWS cloud spend, backed by a vigilant Cost Watch Agent keeping architectures within budget from day one.
Happy building on AWS! ☁️
# aws-amplify# cost-allocation# cost-optimization# agents# serverless
Any opinions in this article are those of the individual author and may not reflect the opinions of AWS.
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