8. Constraints & Assumptions

8.1 Scope Constraints

In Scope

Category	Inclusions	Notes
Property Types	Vacation rentals, short-term rentals	Stays < 30 days
User Types	Guests, Hosts, Property Managers	Plus internal roles
Platforms	Web (responsive), PWA	Mobile-first design
Geography	Global with localization	English first
Booking Types	Direct bookings, OTA sync	No long-term leases
Payments	Credit/debit, bank transfer	Via payment gateway

Out of Scope (MVP)

Category	Exclusions	Rationale
Long-term Rentals	Stays > 30 days	Different regulations
Property Sales	Real estate transactions	Different business model
Native Mobile Apps	iOS/Android native	PWA sufficient for MVP
White-label	Custom branding	Post-MVP feature
Marketplace	Third-party services	Post-MVP feature
Hardware	Smart lock sales/installation	Integration only

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8.2 Technical Constraints

Infrastructure

Constraint	Specification	Rationale
Cloud Provider	Multi-cloud ready	Vendor neutrality
Container Runtime	Docker + Kubernetes	Industry standard
Database	PostgreSQL 16+	ACID, JSON, extensions
Cache	Redis Cluster	Performance, reliability
CDN	Required for media	Global performance
Region	Primary in US, replicas in EU	GDPR compliance

Performance

Constraint	Specification	Measurement
Page Load	< 3 seconds	LCP metric
API Response	< 500ms p95	APM tracking
Search Latency	< 200ms	Elasticsearch
Real-time Messaging	< 3 seconds delivery	WebSocket
Calendar Sync	< 5 minutes	Background jobs
Concurrent Users	1,000 MVP, 100,000 Y3	Load testing

Security

Constraint	Specification	Compliance
Encryption at Rest	AES-256	All databases
Encryption in Transit	TLS 1.3	All connections
PII Encryption	Field-level	Sensitive data
Authentication	OAuth 2.0 + MFA	All users
Session Duration	30 min idle timeout	Configurable
Password Policy	NIST 800-63B	Min 12 chars

Compliance

Constraint	Specification	Implementation
GDPR	Full compliance	EU users
CCPA	Full compliance	California users
PCI DSS	SAQ-A via gateway	Payment data
WCAG	2.1 AA	Accessibility
SOC 2 Type II	Roadmap Year 2	Trust certification

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8.3 Business Constraints

Budget & Resources

Constraint	Specification	Notes
Team Size (MVP)	8-10 FTEs	Cross-functional
Timeline (MVP)	5-6 months	From Phase 0
Infrastructure Cost	$5K-15K/month MVP	Scales with growth
Third-party Services	$2K-5K/month	APIs, tools
Payment Processing	2.9% + $0.30	Standard rates

Revenue Model

Constraint	Specification	Notes
Commission	3-5% from host	Per booking
Service Fee	5-12% from guest	Variable
Premium Features	Subscription model	Post-MVP
API Access	Usage-based	Post-MVP

Partnerships

Constraint	Specification	Impact
OTA Integration	Subject to partner approval	Timeline risk
Payment Gateway	Account approval required	MVP blocker
Insurance	Partnership negotiation	Phase 2
Smart Locks	Partner program enrollment	Phase 2

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8.4 Operational Constraints

Support

Constraint	Specification	Notes
Hours	9am-6pm PST initially	Expand with growth
Channels	Email, in-app chat	Phone post-MVP
SLA	24h response MVP	4h for enterprise
Languages	English only MVP	+10 post-MVP

Uptime

Constraint	Specification	Notes
Availability	99.9% target	8.76 hours/year downtime
Maintenance	Scheduled windows	Off-peak hours
RTO	< 1 hour	Critical systems
RPO	< 15 minutes	Database backups

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8.5 Key Assumptions

Market Assumptions

Assumption	Confidence	Risk if Wrong
Short-term rental market continues growing	High	Reduced TAM
Hosts want alternatives to OTA-only presence	High	Lower adoption
Property managers need better tools	High	Smaller segment
Guests will book direct if pricing is fair	Medium	Conversion issues
AI-powered features add competitive value	Medium	Wasted investment

Technical Assumptions

Assumption	Confidence	Risk if Wrong
Next.js + Node.js can meet performance needs	High	Re-architecture
PostgreSQL scales for our projected volume	High	Migration needed
LLM APIs remain available and affordable	Medium	Feature degradation
OTA APIs remain stable and accessible	Medium	Integration issues
WebSocket scales for real-time messaging	High	Alternative needed

User Assumptions

Assumption	Confidence	Risk if Wrong
Hosts are comfortable with web-based tools	High	Mobile app priority
Hosts will trust AI pricing suggestions	Medium	Feature underused
Guests prefer booking direct for savings	Medium	Conversion issues
Users will adopt MFA for security	Medium	Account security risk
English-only is acceptable for MVP	Medium	Market limitation

Regulatory Assumptions

Assumption	Confidence	Risk if Wrong
GDPR/CCPA requirements are stable	High	Compliance work
No major new STR regulations	Medium	Feature changes
PCI compliance via gateway is sufficient	High	Direct compliance
AI regulations remain manageable	Medium	Feature restrictions

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8.6 Dependencies

External Service Dependencies

Service	Criticality	Fallback
Stripe/Adyen	Critical	Multi-gateway
OpenAI/Anthropic	High	Multi-provider, graceful degradation
Elasticsearch	High	PostgreSQL full-text
Redis	High	PostgreSQL caching
SendGrid/Twilio	High	Multi-provider
Cloudflare	High	Alternative CDN
AWS S3	Medium	Multi-cloud storage

Third-Party API Dependencies

API	Criticality	Fallback
Airbnb API	High	iCal sync
VRBO API	Medium	iCal sync
Booking.com API	Medium	iCal sync
Smart Lock APIs	Medium	Manual code provision
ID Verification	Medium	Manual review
Maps/Geocoding	Medium	Alternative provider

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8.7 Decision Log

Key Architecture Decisions

ID	Decision	Rationale	Date
AD-001	Next.js for frontend	SSR, React ecosystem, DX	-
AD-002	Fastify for backend	Performance, TypeScript	-
AD-003	PostgreSQL primary DB	ACID, JSON, maturity	-
AD-004	Multi-gateway payments	Reliability, rates	-
AD-005	LiteLLM for AI gateway	Multi-provider, fallback	-
AD-006	Kubernetes for orchestration	Scale, vendor-neutral	-
AD-007	Field-level encryption for PII	Privacy compliance	-
AD-008	Cursor-based pagination	Performance at scale	-

Deferred Decisions

ID	Decision	Defer Until	Reason
DD-001	Native mobile apps	Phase 4	PWA sufficient for MVP
DD-002	Self-hosted LLM	Phase 3	Cost/capability analysis
DD-003	Multi-region active-active	Phase 3	Complexity vs need
DD-004	GraphQL subscriptions	Phase 2	WebSocket sufficient

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8.8 Success Criteria

MVP Launch Criteria

Criterion	Target	Measurement
All P0 features complete	100%	Feature checklist
All P1 features complete	80%	Feature checklist
Security audit passed	Yes	Third-party audit
Performance targets met	Yes	Load testing
Zero critical bugs	Yes	Bug tracker
Documentation complete	Yes	Checklist
50 beta users onboarded	Yes	User count

Business Success (6 months post-launch)

Criterion	Target	Measurement
Active listings	2,000	Platform data
Monthly bookings	1,500	Platform data
Host retention	85%	Cohort analysis
Guest repeat rate	20%	Cohort analysis
NPS score	40+	Survey
GMV	$750K/month	Financial data

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8.9 Glossary

Term	Definition
ADR	Average Daily Rate - average revenue per occupied night
GBV	Gross Booking Value - total booking value before fees
GMV	Gross Merchandise Value - total transaction value
LOS	Length of Stay - number of nights per booking
OTA	Online Travel Agency (Airbnb, VRBO, etc.)
PMS	Property Management System
RevPAR	Revenue Per Available Room - ADR × Occupancy Rate
STR	Short-Term Rental
PM	Property Manager
Host	Property owner who lists on the platform
Guest	Person who books a stay
Instant Book	Booking without host approval
Request to Book	Booking requiring host approval
Payout	Funds disbursed to host
Service Fee	Platform fee charged to guest
Commission	Platform fee charged to host