Tradeoffs and Alternatives for Food Delivery Service

Driver Assignment Algorithms

Greedy Assignment (Chosen)

# Assign to nearest available driver
def assign_greedy(order, drivers):
    return min(drivers, key=lambda d: distance(d.location, order.restaurant))

Pros: Fast, simple
Cons: May not optimize globally

Optimal Assignment

# Hungarian algorithm for global optimization
def assign_optimal(orders, drivers):
    cost_matrix = build_cost_matrix(orders, drivers)
    return hungarian_algorithm(cost_matrix)

Pros: Global optimization
Cons: Slower, complex

Location Update Frequency

High Frequency (5 seconds)

• Better tracking accuracy
• Higher battery drain
• More network traffic

Low Frequency (30 seconds)

• Lower battery usage
• Less accurate tracking
• Reduced server load

Database Choices

PostgreSQL + PostGIS (Chosen)

SELECT * FROM restaurants
WHERE ST_DWithin(location, ST_Point($1, $2)::geography, 5000);

Pros: ACID, geospatial support
Cons: Scaling complexity

MongoDB

db.restaurants.find({
  location: {
    $near: {
      $geometry: {type: "Point", coordinates: [lon, lat]},
      $maxDistance: 5000
    }
  }
})

Pros: Flexible schema, horizontal scaling
Cons: Eventual consistency

Real-time Communication

WebSockets (Chosen)

• Bidirectional, low latency
• Persistent connections
• Higher server resources

Server-Sent Events

• Unidirectional, simpler
• Lower resource usage
• No client-to-server push

Polling

• Simple implementation
• Higher latency
• More bandwidth usage

Pricing Models

Fixed Pricing

delivery_fee = base_fee + distance_fee

Pros: Predictable
Cons: No demand adjustment

Dynamic Pricing (Chosen)

delivery_fee = base_fee * demand_multiplier + distance_fee

Pros: Balances supply/demand
Cons: Customer dissatisfaction

Order Matching

First-Come-First-Served

• Simple, fair
• Not optimal for efficiency

Batch Matching (Chosen)

# Match multiple orders every 30 seconds
def batch_match(orders, drivers):
    return optimize_assignments(orders, drivers)

• Better optimization
• Slight delay in assignment

This document covers key tradeoffs in food delivery system design. The next document will explore variations.