newspaper_wedding/.aidlc/knowledge/aidlc-operations-agent/nfr-performance-guide.md

NFR Performance and Scalability Guide

This guide supplements the full NFR Requirements Guide held by the Security Engineer (lead agent for the NFR Requirements stage). It provides the DevOps Engineer with the performance and scalability sections needed for infrastructure-focused contributions during NFR Requirements and NFR Design stages.

Performance Requirement Benchmarking

How to Define Performance Requirements

Every performance requirement must specify:

• Metric: What is being measured (response time, throughput, resource usage)
• Target: The quantitative threshold
• Percentile: Which percentile the target applies to (p50, p95, p99)
• Load condition: Under what concurrency/traffic the target must hold
• Measurement method: How and where the metric is captured

Common Performance Targets by Application Type

Application Type	Metric	Target	Percentile	Notes
Web application (interactive)	Page load time	< 2s	p95	First contentful paint
REST API (synchronous)	Response time	< 200ms	p99	Excludes network transit
Search query	Result delivery	< 500ms	p95	Including ranking
Batch processing	Throughput	N records/min	Average	Define minimum acceptable rate
Real-time messaging	End-to-end latency	< 100ms	p99	From send to delivery
File upload	Processing time	< 5s per MB	p95	Post-upload processing

Performance Anti-Requirements

Explicitly exclude unreasonable expectations:

• "The system should be fast" (not measurable)
• "All pages load instantly" (no target, no percentile)
• "Handle unlimited users" (no capacity boundary)

Replace with: "The dashboard page loads in < 3 seconds at p95 under 500 concurrent users."

Scalability Assessment Frameworks

Capacity Planning Template

Dimension	Current	6-Month Target	12-Month Target	Scaling Mechanism
Concurrent users	N	N * X	N * Y	Horizontal auto-scaling
Data volume	N GB	N * X GB	N * Y GB	Partitioning strategy
Requests per second	N	N * X	N * Y	Load balancer + replicas
Storage growth rate	N GB/month	N * X GB/month	N * Y GB/month	Tiered storage policy

Scalability Requirement Format

NFR-SCALE-NNN: [Scalability Requirement]
Current baseline: [measured current capacity]
Target capacity: [required capacity at specific timeline]
Growth model: [linear, exponential, seasonal, step-function]
Scaling approach: [horizontal, vertical, partitioning, caching]
Cost constraint: [infrastructure cost must remain below $X/month at target scale]
Degradation policy: [what degrades first when approaching capacity limits]

Scaling Decision Matrix

Signal	Scale Up	Scale Out	Optimize First
CPU consistently > 70%	Single-instance workloads	Stateless services	Check for inefficient algorithms
Memory pressure	In-memory processing	Distributed cache	Check for memory leaks
I/O wait > 30%	Faster storage tier	Read replicas, sharding	Query optimization, indexing
Queue depth growing	Faster consumers	More consumer instances	Batch size tuning
Connection pool exhausted	Larger pool size	Connection multiplexing	Connection leak investigation