SlotOptim Engine

Productivity

Original Idea

Appointment Slot Optimizer A background service that learns demand patterns and auto-fills gaps with waitlist offers and smart buffers.

Product Requirements Document: SlotOptim Engine (v1.0)

1. Executive Summary

The SlotOptim Engine is an intelligent background service designed to eliminate the "Swiss cheese effect" in professional calendars. By leveraging real-time calendar fragment analysis and machine learning, the system identifies underutilized time gaps and automatically orchestrates waitlist notifications to fill them. It maximizes revenue for service-based businesses (medical, legal, wellness) by converting fragmented downtime into billable appointments while dynamically managing buffers to prevent staff burnout.

2. Problem Statement

Service-based businesses lose 15–25% of potential revenue due to:

  • Fragmented Gaps: Small, unbookable 15–45 minute slivers between appointments.
  • Manual Latency: Staff cannot react fast enough to fill a last-minute cancellation.
  • Static Buffers: Uniform rest periods that don't account for service complexity or predicted delays, leading to cascading schedule drift.
  • Unmanaged Waitlists: Static lists that require manual phone calls, which customers often miss.

3. Goals & Success Metrics

  • Increase Calendar Utilization: Target a 12% increase in billable hours per provider.
  • Reduce Gap Response Time: Move from manual notification (hours) to automated "Flash Slot" offers (seconds).
  • Revenue Recovery: Track total dollar value of slots filled via the Optimizer.
  • User Retention: Achieve <5% churn by proving ROI via a Revenue Recovery Dashboard.

4. User Personas

  • Dr. Sarah (Medical Practice Manager): Needs to keep 4 doctors' schedules full. Overwhelmed by cancellations and HIPAA compliance requirements.
  • James (High-end Salon Owner): Focused on maximizing "chair time" and offering a premium, tech-forward experience to clients.
  • Alex (The Waitlisted Customer): Wants an earlier appointment but doesn't want to call back repeatedly. Values "first-come, first-served" transparency.

5. User Stories

  • As a Practice Manager, I want the system to detect a 45-minute gap so that it can automatically offer it to the top 5 qualified waitlisted patients.
  • As a Provider, I want "Smart Buffers" to increase after complex surgeries so that I don't run late for subsequent patients.
  • As a Customer, I want to receive a WhatsApp link for a newly opened slot so I can book it instantly with one click.
  • As a Business Owner, I want to see a heatmap of demand patterns so I can adjust my staff's working hours to match peak interest.

6. Functional Requirements

6.1. Real-time Gap Detection

  • Analyze Google/Microsoft calendars using webhook-driven delta sync.
  • Identify "Unproductive Gaps" (shorter than the minimum service time).
  • Flag "High-Risk Slots" based on predictive no-show scoring.

6.2. Automated Waitlist Orchestration

  • Flash Slot Logic: Trigger SMS/WhatsApp notifications to waitlisted users when a gap opens.
  • Atomic Booking: Use Redis distributed locking to ensure "First-to-Click" wins without double-booking.
  • Priority Weighting: Sort waitlist offers by customer loyalty, service value, or time-on-list.

6.3. Smart Buffer Management

  • Dynamic adjustment of post-appointment "cooldown" periods.
  • Service-aware buffers (e.g., +15 mins for new patients, +0 for follow-ups).

6.4. Predictive Analytics (ML)

  • Predict no-show probability for every booking.
  • Suggest "Overbooking" only when the aggregate risk score exceeds a safety threshold.

7. Technical Requirements

7.1. Core Tech Stack (2026 Standards)

  • Backend: FastAPI (2026 Stable) utilizing Pydantic V2 (Rust Engine) and uvloop.
  • Frontend: Next.js 15 (App Router) with React 19 and Tailwind CSS V4.
  • Database: PostgreSQL 17+ with btree_gist for time-range indexing.
  • Real-time/Locking: Redis 7.4+ for Lua-based atomic locking.
  • Identity: Auth0 (Okta) with Fine-Grained Authorization (FGA) for HIPAA/B2B isolation.
  • Compute: AWS ECS Fargate on Graviton4 processors.

7.2. External Integrations

  • Calendar: Google Calendar API (Incremental Sync) & Microsoft Graph API (Delta Queries).
  • Communication: Twilio for SMS/WhatsApp via SQS-buffered workers.
  • Payments: Stripe for "No-show protection" deposits.

8. Data Model

| Entity | Key Attributes | Relationships | | :--- | :--- | :--- | | Provider | id, org_id, timezone, min_gap_config | 1:N Appointments | | Appointment | id, time_range (tstzrange), service_type, no_show_risk | M:1 Provider | | WaitlistEntry | id, user_contact, preferred_ranges, priority | M:1 Org | | SlotGap | id, start, end, status (Open/Filled/Expired) | 1:1 Triggering Cancellation |

9. API Specification (Highlights)

GET /v1/gaps/analyze

  • Purpose: Force a scan for a specific provider's fragments.
  • Response: 200 OK with List[GapObject].

POST /v1/waitlist/offer

  • Payload: { "gap_id": "uuid", "strategy": "priority_burst" }
  • Action: Triggers the Step Functions workflow to notify users.

POST /v1/bookings/instant-claim

  • Payload: { "slot_token": "jwt", "customer_id": "id" }
  • Mechanism: Uses Redis SETNX with a 300s TTL to hold the slot during checkout.

10. UI/UX Requirements

  • Operational Command Center: A Next.js dashboard using Container Queries (@container) to ensure widgets work in any layout.
  • Capacity Heatmap: Recharts-based visualization of "Fragile Timespaces" (areas of high cancellation risk).
  • Skeleton States: Mandatory use of React Suspense for all asynchronous data widgets.

11. Non-Functional Requirements

  • Latency: Gap analysis must complete in <200ms using optimized interval arithmetic (NumPy/Polars).
  • Concurrency: Support 10,000+ SMS notifications in a 60-second burst using AWS Step Functions Distributed Map.
  • Compliance: SOC2 Type II and HIPAA-compliant data encryption at rest (AES-256) and in transit (TLS 1.3).

12. Out of Scope

  • Building a full Electronic Medical Record (EMR) system.
  • Handling physical room/equipment scheduling (V1 focuses on staff time only).
  • Direct payroll processing.

13. Risks & Mitigations

  • Risk: API Throttling from Google/Microsoft.
    • Mitigation: Implement Push-Triggered Delta Sync with exponential backoff.
  • Risk: Double-booking during high-traffic "Flash Slot" claims.
    • Mitigation: Mandatory Redis Lua scripts for atomic "Check-and-Set" logic.
  • Risk: SMS Fatigue.
    • Mitigation: User-level "Quiet Hours" and frequency capping in the notification engine.

14. Implementation Tasks

Phase 1: Project Setup & Infrastructure

  • [ ] Initialize FastAPI 2026 project with Pydantic V2 and uvloop
  • [ ] Set up Next.js 15 (App Router) with Tailwind CSS V4 and shadcn/ui
  • [ ] Configure Auth0 Organizations for multi-tenant identity management
  • [ ] Provision AWS RDS (PostgreSQL 17) and enable btree_gist extension

Phase 2: Calendar & Gap Logic

  • [ ] Implement Google/Microsoft OAuth 2.0 flow with limited scopes
  • [ ] Build the "Fragment Analysis" engine using Python interlap library
  • [ ] Create PostgreSQL EXCLUDE constraints to prevent overlapping time ranges
  • [ ] Implement Webhook handlers for Google watch and MS Graph delta

Phase 3: Waitlist & Atomic Booking

  • [ ] Develop the Redis-based "Hold-then-Confirm" state machine
  • [ ] Implement Lua scripts for atomic slot acquisition
  • [ ] Set up AWS Step Functions Distributed Map for high-burst SMS triggers
  • [ ] Build the "Instant Claim" deep-link landing page (React 19)

Phase 4: Machine Learning & Analytics

  • [ ] Train XGBoost model for no-show prediction on anonymized historical data
  • [ ] Integrate Meta's Prophet for weekly demand forecasting
  • [ ] Build the "Revenue Recovery" dashboard with Recharts
  • [ ] Implement SOCI (Seekable OCI) on ECS Fargate for sub-10s task scaling

Phase 5: Hardening & Compliance

  • [ ] Conduct load testing (target: 20k RPS on gap detection)
  • [ ] Implement HIPAA-compliant audit logging for all calendar modifications
  • [ ] Finalize "Smart Buffer" logic with service-category weights
  • [ ] Execute automated penetration testing on Auth0 FGA boundaries