Inventory Management

Real-time flight inventory, availability, and capacity control systems. Uses a Classless Numerical Model (P1-P5) replacing the legacy 26-character booking class system.

Scope

Core Functions

Seat inventory management (physical and virtual)
Numerical tier availability (P1-P5)
10-minute inventory holds during checkout
Overbooking policies and limits
Waitlist management

Inventory Types

Leg-based: Physical seats per flight segment
Segment-based: O&D (Origin-Destination) availability
Tier-based: Numerical price tiers (P1-P5)

Numerical Tier Model (P1-P5)

The Classless Philosophy

Abandoning the legacy 26 booking classes (A-Z RBDs) for a simpler numerical model:

┌─────────────────────────────────────────────────────────────────┐
│                                                                 │
│                    P5 (Highest Fare)                            │
│                   ┌───────────┐                                 │
│                   │           │                                 │
│              P4   │           │                                 │
│             ┌─────┴───┐       │                                 │
│             │         │       │                                 │
│        P3   │         │       │     Availability at P5          │
│       ┌─────┴───┐     │       │     automatically unlocks       │
│       │         │     │       │     P1-P4                       │
│  P2   │         │     │       │                                 │
│ ┌─────┴───┐     │     │       │                                 │
│ │         │     │     │       │                                 │
│ │   P1    │     │     │       │                                 │
│ │(Lowest) │     │     │       │                                 │
│ └─────────┴─────┴─────┴───────┘                                 │
│                                                                 │
└─────────────────────────────────────────────────────────────────┘

Tier Definitions

Tier	Fare Level	Availability Rule	Typical Use
P1	Lowest	Only when P5 available	Promo/sale fares
P2	Low	When P4+ available	Early booking
P3	Medium	When P3+ available	Standard economy
P4	High	When P2+ available	Flexible fares
P5	Highest	Always (if seats exist)	Last-minute/premium

Cascading Availability Rule

"Availability at P5 automatically unlocks P1-P4"

This simplifies Revenue Management:

No complex nesting logic across 26 classes
Clear tier progression
RM system sets availability at each tier
Lower tiers only open when higher tiers have inventory

Nested Booking Limits

Control inventory at each tier with nested protection:

┌─────────────────────────────────────────────────────────────────┐
│                 NESTED BOOKING LIMITS                           │
├─────────────────────────────────────────────────────────────────┤
│                                                                 │
│  Aircraft Capacity: 180 seats                                   │
│                                                                 │
│  ┌─────────────────────────────────────────────────────────┐   │
│  │ P5 Authorization: 180 (full plane available)             │   │
│  │  ┌──────────────────────────────────────────────────┐   │   │
│  │  │ P4 Authorization: 150 (30 protected for P5)       │   │   │
│  │  │  ┌───────────────────────────────────────────┐   │   │   │
│  │  │  │ P3 Authorization: 100 (50 protected P4+)   │   │   │   │
│  │  │  │  ┌────────────────────────────────────┐   │   │   │   │
│  │  │  │  │ P2 Authorization: 50 (50 for P3+)   │   │   │   │   │
│  │  │  │  │  ┌─────────────────────────────┐   │   │   │   │   │
│  │  │  │  │  │ P1 Authorization: 20 (promo) │   │   │   │   │   │
│  │  │  │  │  └─────────────────────────────┘   │   │   │   │   │
│  │  │  │  └────────────────────────────────────┘   │   │   │   │
│  │  │  └───────────────────────────────────────────┘   │   │   │
│  │  └──────────────────────────────────────────────────┘   │   │
│  └─────────────────────────────────────────────────────────┘   │
│                                                                 │
│  P1 sells out → P2 still has 30 seats (50-20)                   │
│  P2 sells out → P3 still has 50 seats (100-50)                  │
│  ...and so on                                                   │
│                                                                 │
└─────────────────────────────────────────────────────────────────┘

Tier	Authorization	Protected Seats	Available After Lower Tiers
P1	20	-	20
P2	50	30 from P1	50
P3	100	50 from P1+P2	100
P4	150	50 from P1-P3	150
P5	180	30 from P1-P4	180

Revenue Management sets these limits dynamically based on:

Demand forecast
Days to departure
Historical load factors
Competitor pricing

10-Minute Hold Window

┌─────────────────────────────────────────────────────────────────┐
│                                                                 │
│   Customer selects flight → Inventory HELD (10 minutes)         │
│                                                                 │
│   ┌─────────┐                                                   │
│   │  Redis  │ ◄── Sub-millisecond inventory lock                │
│   │  Cache  │     during checkout                               │
│   └─────────┘                                                   │
│                                                                 │
│   If payment completed → Inventory SOLD                         │
│   If timeout (10 min) → Inventory RELEASED                      │
│                                                                 │
│   Prevents overselling during checkout window                   │
│                                                                 │
└─────────────────────────────────────────────────────────────────┘

Implementation:

Redis cache for real-time deduct
Sub-millisecond inventory locking
Automatic release after 600 seconds
Prevents phantom inventory blocking

Data Model

Updated for Numerical Tiers

Flight
├── FlightNumber, Date, Route
├── Legs[]
│   ├── DepartureStation, ArrivalStation
│   ├── Aircraft, Capacity
│   └── PriceTiers[]
│       ├── Tier (1-5)
│       ├── AuthorizedCapacity
│       ├── SoldCount
│       ├── HeldCount
│       └── Available
└── Segments[] (O&D combinations)

Prisma Schema

model FlightInventory {
  id              String    @id @default(uuid()) @db.Uuid
  flightNumber    String
  flightDate      DateTime  @db.Date
  legOrigin       String    @db.VarChar(3)
  legDestination  String    @db.VarChar(3)

  priceTier       Int       // 1-5
  authorized      Int       // Capacity at this tier
  sold            Int       @default(0)
  held            Int       @default(0)

  updatedAt       DateTime  @updatedAt

  @@unique([flightNumber, flightDate, legOrigin, legDestination, priceTier])
  @@index([flightNumber, flightDate])
}

model InventoryHold {
  id              String    @id @default(uuid()) @db.Uuid
  orderId         String    @db.Uuid
  flightKey       String    // composite key
  priceTier       Int
  quantity        Int

  expiresAt       DateTime  // 10 min from creation
  createdAt       DateTime  @default(now())

  @@index([expiresAt])
  @@index([orderId])
}

Performance Requirements

Metric	Target
Availability query	<50ms
Inventory lock	<1ms (sub-millisecond)
Hold creation	<10ms
Concurrent searches	1000+
Hold window	10 minutes (600 seconds)

Consistency Model

Display: Eventual consistency acceptable (cached)
Booking: Strong consistency required (real-time)
Holds: Atomic operations via Redis

Caching Strategy (Redis)

┌─────────────────────────────────────────────────────────────────┐
│                      Redis Cache Layer                          │
├─────────────────────────────────────────────────────────────────┤
│                                                                 │
│  availability:{flight}:{date}:{leg}                             │
│  ├── P1: 5                                                      │
│  ├── P2: 12                                                     │
│  ├── P3: 25                                                     │
│  ├── P4: 40                                                     │
│  └── P5: 50                                                     │
│                                                                 │
│  holds:{flight}:{date}:{leg}:{tier}                             │
│  └── Set of order IDs with expiry                               │
│                                                                 │
│  TTL: 60 seconds for availability                               │
│  Invalidation: On booking confirmation                          │
│                                                                 │
└─────────────────────────────────────────────────────────────────┘

Integration Points

System	Direction	Data
OMS	Bidirectional	Holds, sold updates
Offer Engine	Outbound	Availability by tier
Revenue Management	Inbound	Tier limits, overbooking
Schedule	Inbound	Flight creation, capacity
DCS	Outbound	Checked-in counts
NDC	Outbound	Availability responses

Research Topics

Redis cluster configuration for inventory
Hold expiration cleanup strategies
Overbooking optimization per tier
Real-time availability streaming
Multi-region inventory consistency
Waitlist management by tier

Legacy Reference (26 RBDs)

For backward compatibility with GDS systems (if needed):

RBD	Typical Tier Mapping
F, A	P5 (Premium)
J, C, D	P4-P5 (Business)
Y, B, M	P3-P4 (Full Economy)
H, K, L	P2-P3 (Discount)
Q, V, W	P1-P2 (Deep Discount)

Note: This mapping is for legacy interoperability only. The primary model uses P1-P5 tiers.