Chapter 24: Implementation Roadmap

Overview

This chapter presents the complete implementation roadmap for the POS platform, organized into 4 phases spanning 16 weeks. Each phase builds upon the previous, with clear milestones and dependencies.

Phase Summary

Phase	Name	Duration	Key Deliverables
1	Foundation	Weeks 1-4	Multi-tenant, Auth, Catalog
2	Core	Weeks 5-10	Inventory, Sales, Payments, Cash
3	Support	Weeks 11-14	Customers, Offline, RFID
4	Production	Weeks 15-16	Monitoring, Security, Deployment

Gantt Chart

Week:     1    2    3    4    5    6    7    8    9   10   11   12   13   14   15   16
          |----|----|----|----|----|----|----|----|----|----|----|----|----|----|----|----|

PHASE 1 - FOUNDATION
Multi-Tenant   [====|====]
Authentication      [====|====]
Catalog                  [====|====]

PHASE 2 - CORE
Inventory                      [====|====]
Sales Domain                        [====|====]
Payments                                 [====|====]
Cash Drawer                                   [====|====]

PHASE 3 - SUPPORT
Customer/Loyalty                                    [====|====]
Offline Sync                                             [====|====]
RFID Module                                                   [====|====]

PHASE 4 - PRODUCTION
Monitoring                                                          [====]
Security                                                             [====]
Deployment                                                                [====]

MILESTONES
    M1: Tenant Demo        *
    M2: Auth Complete           *
    M3: Catalog API                  *
    M4: Inventory Sync                    *
    M5: First Sale                             *
    M6: Payment Complete                            *
    M7: Offline Ready                                         *
    M8: Go-Live                                                          *

Phase 1: Foundation (Weeks 1-4)

Week 1-2: Multi-Tenant Infrastructure

Objective: Establish schema-per-tenant database isolation with automatic provisioning.

Day	Task	Deliverable
1-2	Tenant entity and repository	Tenant CRUD operations
3-4	Schema provisioning service	Automatic schema creation
5	Tenant resolution middleware	Request-scoped tenant context
6-7	Connection string routing	Dynamic connection per tenant
8-9	Tenant management API	REST endpoints for tenants
10	Integration tests	Tenant isolation verified

Claude Commands:

/dev-team implement tenant entity with repository pattern
/architect-review multi-tenant database isolation strategy
/dev-team create tenant provisioning service
/dev-team implement tenant resolution middleware
/qa-team write tenant isolation integration tests

Success Criteria:

New tenant creates isolated schema in < 5 seconds
Tenant data completely isolated (cross-tenant queries blocked)
Tenant context available in all service layers
100% test coverage on tenant resolution

Week 2-3: Authentication System

Objective: Implement JWT-based authentication with PIN support for POS terminals.

Day	Task	Deliverable
1-2	User entity with password hashing	BCrypt password storage
3-4	JWT token service	Access + refresh token generation
5-6	PIN-based authentication	4-6 digit PIN for terminals
7-8	RBAC permission system	Role-based access control
9-10	Auth middleware	Token validation, user context

Claude Commands:

/dev-team implement user entity with bcrypt password hashing
/dev-team create JWT token service with refresh token support
/dev-team implement PIN authentication for POS terminals
/security-review authentication implementation
/dev-team create authorization middleware with RBAC

Success Criteria:

JWT tokens expire and refresh correctly
PIN login works for cashier terminals
Roles enforce API access restrictions
Password reset flow functional
Failed login attempts are rate-limited

Week 3-4: Catalog Domain

Objective: Build product catalog with variants, categories, and pricing.

Day	Task	Deliverable
1-2	Product and Category entities	Domain models
3-4	Product variant support	Size, color, style variations
5-6	Pricing rules engine	Base price, markups, promotions
7-8	Product repository	CRUD with search, filtering
9-10	Catalog API endpoints	REST API for products

Claude Commands:

/dev-team create product entity with variant support
/dev-team implement category hierarchy with nested sets
/dev-team create pricing rules engine
/dev-team implement product repository with full-text search
/dev-team create catalog API endpoints with pagination

Success Criteria:

Products support unlimited variants
Categories support infinite nesting
Full-text search returns results in < 100ms
Bulk import handles 10,000 products
API returns paginated results

Phase 2: Core (Weeks 5-10)

Week 5-6: Inventory Domain

Objective: Implement multi-location inventory with real-time tracking.

Day	Task	Deliverable
1-2	Inventory item entity	Stock levels per location
3-4	Stock movement tracking	Audit trail of all changes
5-6	Inventory adjustment service	Manual adjustments with reasons
7-8	Inter-store transfers	Transfer request workflow
9-10	Low stock alerts	Configurable thresholds

Claude Commands:

/dev-team create inventory item entity with location quantities
/dev-team implement stock movement event sourcing
/dev-team create inventory adjustment service
/dev-team implement inter-store transfer workflow
/dev-team create low stock alert notification system

Dependencies: Catalog (products), Multi-tenant (locations)

Success Criteria:

Stock levels accurate across all locations
Every inventory change has audit record
Transfers update both source and destination
Alerts fire when stock below threshold
Concurrent updates handled correctly

Week 6-7: Sales Domain (Event Sourcing)

Objective: Build sale transaction processing with event-sourced state.

Day	Task	Deliverable
1-2	Sale aggregate root	Event-sourced sale entity
3-4	Sale events	ItemAdded, ItemRemoved, DiscountApplied
5-6	Sale projections	Current cart state, totals
7-8	Sale completion	Finalization workflow
9-10	Receipt generation	Digital and print receipts

Claude Commands:

/dev-team create sale aggregate with event sourcing
/dev-team implement sale events (add, remove, discount)
/dev-team create sale projection service
/dev-team implement sale completion workflow
/dev-team create receipt generation service

Dependencies: Inventory (stock deduction), Catalog (product lookup)

Success Criteria:

Sales can be reconstructed from events
Cart updates in < 50ms
Tax calculations accurate to penny
Concurrent cart modifications handled
Receipts generated in < 1 second

Week 8-9: Payment Processing

Objective: Implement multi-tender payment with gateway integration.

Day	Task	Deliverable
1-2	Payment entity	Multi-tender support
3-4	Cash payment handler	Exact, over, change calculation
5-6	Card payment abstraction	Payment gateway interface
7-8	Split tender support	Multiple payment methods
9-10	Void and refund	Transaction reversal

Claude Commands:

/dev-team create payment entity with multi-tender support
/dev-team implement cash payment handler with change calculation
/dev-team create payment gateway abstraction (Stripe/Square)
/dev-team implement split tender payment processing
/dev-team create void and refund transaction handlers

Dependencies: Sales (total calculation)

Success Criteria:

Cash, card, and mixed payments work
Change calculated correctly
Failed payments don’t affect inventory
Refunds trace to original sale
Gateway timeouts handled gracefully

Week 9-10: Cash Drawer Operations

Objective: Manage physical cash with drawer sessions and blind counts.

Day	Task	Deliverable
1-2	Drawer session entity	Open, active, closed states
3-4	Cash in/out tracking	Expected vs actual
5-6	Blind count support	Cashier cannot see expected
7-8	Drawer reconciliation	Variance calculation
9-10	Shift handoff	Mid-shift cash pickup

Claude Commands:

/dev-team create drawer session entity with state machine
/dev-team implement cash transaction tracking
/dev-team create blind count entry service
/dev-team implement drawer reconciliation with variance alerts
/dev-team create shift handoff workflow

Dependencies: Authentication (cashier identity), Sales (cash payments)

Success Criteria:

Drawer opens with starting balance
All cash movements tracked
Blind count mode prevents cheating
Variances flagged for review
Shift reports accurate

Phase 3: Support (Weeks 11-14)

Week 11-12: Customer Domain with Loyalty

Objective: Customer profiles, purchase history, and loyalty points.

Day	Task	Deliverable
1-2	Customer entity	Profile, contact info
3-4	Customer lookup	Phone, email, loyalty ID
5-6	Purchase history	Orders linked to customer
7-8	Loyalty program	Points earning and redemption
9-10	Customer API	CRUD and search endpoints

Claude Commands:

/dev-team create customer entity with contact information
/dev-team implement customer lookup by phone, email, ID
/dev-team create purchase history tracking
/dev-team implement loyalty points system
/dev-team create customer API with search

Dependencies: Sales (purchase linkage)

Success Criteria:

Customer lookup in < 200ms
Points calculated on every purchase
Points redemption decreases balance
Purchase history complete
GDPR data export works

Week 12-13: Offline Sync Infrastructure

Objective: Enable POS operation during network outages.

Day	Task	Deliverable
1-2	Local SQLite database	Offline storage
3-4	Queue service	Offline transaction queue
5-6	Sync protocol	Conflict resolution
7-8	Connectivity detection	Online/offline mode
9-10	Background sync	Automatic upload when online

Claude Commands:

/dev-team implement local SQLite storage for offline mode
/dev-team create offline transaction queue service
/dev-team implement sync protocol with conflict resolution
/dev-team create connectivity detection service
/dev-team implement background sync with retry logic

Dependencies: Sales, Payments, Inventory

Success Criteria:

POS operates fully offline
Transactions queue locally
Sync completes within 30 seconds online
Conflicts resolved with last-write-wins
No data loss during sync

Week 13-14: RFID Module (Optional)

Objective: RFID tag reading for inventory and sales.

Day	Task	Deliverable
1-2	RFID reader abstraction	Device interface
3-4	Tag inventory scanning	Bulk inventory count
5-6	POS tag reading	Add items by RFID
7-8	Anti-theft detection	Unpaid item alerts
9-10	Tag encoding	Write product info to tags

Claude Commands:

/dev-team create RFID reader abstraction interface
/dev-team implement bulk inventory scanning with RFID
/dev-team create POS RFID tag reading for sales
/dev-team implement anti-theft detection at exit
/dev-team create RFID tag encoding service

Dependencies: Inventory, Catalog

Success Criteria:

Reader connects and reads tags
Bulk scan counts 1000 items in < 60 seconds
POS adds items by RFID instantly
Alerts fire for unpaid items
Tags written with product data

Phase 4: Production (Weeks 15-16)

Week 15: Monitoring and Alerting

Objective: Production observability with metrics, logs, and alerts.

Day	Task	Deliverable
1	Structured logging	Serilog with context
2	Metrics collection	Prometheus endpoints
3	Health checks	Liveness and readiness
4	Grafana dashboards	Key metrics visualization
5	Alert rules	PagerDuty/Slack integration

Claude Commands:

/dev-team implement structured logging with Serilog
/dev-team add Prometheus metrics endpoints
/dev-team create health check endpoints
/devops-team create Grafana dashboards
/devops-team configure alerting rules

Success Criteria:

Logs include correlation IDs
Key metrics exposed (latency, errors, saturation)
Health checks report component status
Dashboards show real-time data
Alerts notify on-call team

Week 15: Security Hardening

Objective: Production security controls and compliance.

Day	Task	Deliverable
1	Input validation	All endpoints validated
2	Rate limiting	API throttling
3	Secrets management	Vault integration
4	Security headers	CSP, HSTS, etc.
5	Penetration testing	Vulnerability scan

Claude Commands:

/security-team review input validation coverage
/dev-team implement rate limiting middleware
/devops-team configure secrets management with Vault
/dev-team add security headers middleware
/security-team run penetration test scan

Success Criteria:

No SQL injection vulnerabilities
Rate limiting prevents abuse
No secrets in code or logs
Security headers configured
Pen test findings remediated

Week 16: Production Deployment

Objective: Deploy to production with zero-downtime release.

Day	Task	Deliverable
1-2	Production infrastructure	Kubernetes/Docker Swarm
3	Database migration	Schema applied
4	Blue-green deployment	Zero-downtime release
5	Go-live	Production traffic

Claude Commands:

/devops-team provision production infrastructure
/devops-team run database migrations
/devops-team execute blue-green deployment
/qa-team run production smoke tests
/team go-live celebration

Success Criteria:

Infrastructure provisioned and tested
Database migrated without data loss
Deployment completes in < 10 minutes
Zero downtime during release
Production accepting traffic

Module Dependencies

                    ┌─────────────┐
                    │ Multi-Tenant│
                    └──────┬──────┘
                           │
           ┌───────────────┼───────────────┐
           │               │               │
    ┌──────▼──────┐ ┌──────▼──────┐ ┌──────▼──────┐
    │    Auth     │ │   Catalog   │ │  Locations  │
    └──────┬──────┘ └──────┬──────┘ └──────┬──────┘
           │               │               │
           │        ┌──────▼──────┐        │
           │        │  Inventory  │◄───────┘
           │        └──────┬──────┘
           │               │
    ┌──────▼───────────────▼──────┐
    │           Sales             │
    └──────┬───────────────┬──────┘
           │               │
    ┌──────▼──────┐ ┌──────▼──────┐
    │  Payments   │ │  Customer   │
    └──────┬──────┘ └─────────────┘
           │
    ┌──────▼──────┐
    │ Cash Drawer │
    └─────────────┘

    ┌─────────────┐
    │    RFID     │ (Optional, independent)
    └─────────────┘

    ┌─────────────┐
    │ Offline Sync│ (Wraps: Sales, Payments, Inventory)
    └─────────────┘

Risk Assessment

High Risk

Risk	Impact	Mitigation
Multi-tenant data leak	Critical	Extensive testing, schema isolation
Payment processing failure	High	Retry logic, fallback methods
Offline sync data loss	High	Local backup, conflict resolution

Medium Risk

Risk	Impact	Mitigation
Performance degradation	Medium	Load testing, caching
RFID reader compatibility	Medium	Abstraction layer
Third-party API outages	Medium	Circuit breakers, fallbacks

Low Risk

Risk	Impact	Mitigation
UI complexity	Low	User testing, iteration
Documentation gaps	Low	Continuous documentation

Resource Requirements

Team Composition

Role	Count	Phase Focus
Senior Backend Developer	2	All phases
Frontend Developer	1	Phase 2-3
DevOps Engineer	1	Phase 1, 4
QA Engineer	1	All phases
Project Manager	1	All phases

Infrastructure

Resource	Development	Production
API Servers	1	3 (min)
Database	Shared	Dedicated cluster
Cache	Shared	Dedicated Redis
Message Queue	Shared	Dedicated RabbitMQ

Milestone Checklist

M1: Tenant Demo (Week 2)

Tenant CRUD API working
Schema provisioning automated
Tenant isolation verified

M2: Auth Complete (Week 3)

User registration and login
JWT tokens functioning
PIN login for terminals

M3: Catalog API (Week 4)

Product CRUD complete
Variant support working
Search and filtering

M4: Inventory Sync (Week 6)

Stock levels tracked
Movements audited
Transfers working

M5: First Sale (Week 7)

Cart operations complete
Sale finalization working
Inventory decremented

M6: Payment Complete (Week 9)

Multi-tender payments
Card processing
Refunds working

M7: Offline Ready (Week 13)

Offline mode functional
Sync protocol tested
Conflict resolution verified

M8: Go-Live (Week 16)

Production deployed
Monitoring active
Team trained

Next Steps

Begin Chapter 25: Phase 1 Foundation for detailed week-by-week implementation
Set up project tracking in GitHub Projects or Jira
Schedule weekly demo sessions for stakeholder feedback
Establish on-call rotation for Phase 4

Chapter 24 Complete - Implementation Roadmap

Keyboard shortcuts

The POS Platform Blueprint