fast-decision 0.2.5

High-performance rule engine

fast-decision

A high-performance rule engine written in Rust with Python bindings, designed for applications that need to evaluate complex business rules with minimal latency and maximum throughput.

Features

• High Performance: Rust-powered engine with zero-cost abstractions
• Priority-based Evaluation: Rules sorted by priority (lower number = higher priority)
• Stop-on-First: Per-category flag to stop after first match
• Condition Operators: Familiar syntax with $equals, $not-equals, $greater-than, $less-than, $greater-than-or-equals, $less-than-or-equals, $and, $or
• Complex Logic: Support for nested AND/OR predicates
• Python Bindings: Native performance with idiomatic Python API via PyO3
• Memory Efficient: Minimal allocations in hot path, optimized data structures
• Benchmarked: Built-in performance benchmarks with Criterion

Use Cases

Fast Decision is ideally suited for systems where performance and low decision latency are critical.

1. Core Business Logic and Processes

• Business Rule Engines (Classical rule systems for decision automation)
  • Transaction Approval/Rejection (Fast checking of conditions for immediate decisions, e.g., limits or stop-lists).
  • Commission and Fee Calculation (Determining the exact amount based on customer type, region, and transaction volume).
  • Management of Complex Contract Conditions (Automating the verification of product or service compliance with contract terms).
• Workflow Automation
  • Document Routing (Directing a request for approval to the correct department based on amount, document type, or initiator's role).
  • Task Status Management (Automatic transition of a task to "Awaiting Review" status upon fulfillment of all preceding conditions).

2. Financial and Commercial

• Dynamic Pricing Systems
  • Real-time Discount Calculation (Applying complex discount rules based on purchase history, loyalty level, inventory, and current promotions).
  • Product Pricing Tier Determination (Instant assignment of a category based on product characteristics, critical for high-volume E-commerce).
• Credit Scoring and Underwriting (Fast risk assessment)
  • Initial Application Scoring (Immediate filtering of applications that do not meet minimum criteria, using "Stop-on-First" logic for high performance).
  • Fraud Detection (Rapid assessment of transaction patterns in real-time before processing).

3. Security and Authorization

• Access Control and Authorization (ABAC) (Access management based on roles and attributes)
  • User Rights Determination (Granting access to a resource based not only on role but also on attributes: time of day, IP address, subscription level).
  • API Request Control (Quick verification of every incoming request against allowed limits and conditions).
• Feature Flags and A/B Testing
  • Feature Toggling (Determining which version of a feature a specific user should be shown, based on their ID, geography, or registration date).
  • Traffic Splitting (Directing 10% of traffic to a new, experimental version of a service).

4. Data and Infrastructure

• Data Validation and Filtering
  • Input Data Cleansing (Fast checking and discarding of incomplete or incorrect records before saving them to the database).
  • Event Routing (Directing events from a general stream like Kafka/RabbitMQ to a specific handler based on event type or criticality).
• Configuration and Settings (Decision making for system configuration)
  • System Configuration Determination (Selecting optimal service startup parameters based on environment, load, or other input data).
  • Alerting and Monitoring (Triggering alerts only when a combination of multiple conditions is met: high CPU load AND low disk space).

5. Development and Code Governance

• Priority-based Execution
  • Cascading Rule Application (For example, first applying a "Global Ban," then a "Special Permission," using numerical priorities).
  • Stop on First Match (Using the "Stop-on-First" flag to boost performance in categories where one successful rule is sufficient).
• Python Bindings (Using the Rust engine within the Python ecosystem)
  • Integration with Django/Flask (Using a high-performance Rule Engine for critical logic in standard Python applications).
  • Fast Processing in Data Science (Applying rules to large data dictionaries for quick labeling or filtering before feeding into an ML model).

6. Telecommunications and IoT (Telecom & Internet of Things)

• Real-time Data Processing (Processing data in real-time with low latency)
  • Sensor Data Filtering (Rapidly discarding noise or incorrect readings from IoT sensors directly at the edge network).
  • Network Traffic Routing (Making decisions on packet direction based on IP addresses, ports, or protocols with minimal delay).
• Edge Computing Decisions (Decision making at the network edge)
  • Autonomous Device Actions (Local decision making by an IoT device (e.g., turn a pump on/off) without relying on the central cloud, based on local rules).

7. Gaming Industry

• Anti-Cheat Logic
  • Instant Verification of Suspicious Actions (Applying complex logic to detect unnatural player action patterns in real-time).
• In-Game Events and Rewards
  • Reward Triggers (Automatic crediting of bonuses or initiation of events upon the fulfillment of a combination of in-game conditions).

8. Government Sector and Compliance

• Regulatory Compliance Checks
  • Automatic Form Verification (Quickly determining if an application meets all governmental or internal regulatory requirements before submission).
• Eligibility Determination
  • Criteria Calculation (Instantly determining whether a citizen is entitled to a specific service or benefit based on input data).

9. ML Optimization

• Pre-Processing Filters
  • Low-Quality Data Exclusion (Quickly discarding records that may introduce noise into the model before they enter the training pipeline, saving computational resources).
  • Basic Segmentation (Using rules to separate the incoming data stream by type before feeding them into specialized models).
• Model Switching and Orchestration
  • Model Version Switching (Deciding which version of an ML model to use—old stable or new experimental—based on input parameters, such as region or risk level).

10. Content Management Systems (CMS)

• Content Personalization
  • Dynamic Page Layout (Determining which ad banner, article, or product should be shown to a user based on their session, device, and browsing history).
  • Automatic Moderation (Rapid verification of user-generated content—comments, listings—for compliance with stop-words, publishing frequency, or other rules, prior to manual review).

11. System Integration and Migration

• Data Mapping and Transformation
  • Format Conversion (Using rules to transform a complex JSON event from a legacy system into the format required by a new system, for example, changing field names or merging values).
• Legacy System Decoupling
  • "Shadow" Logic Execution (Running new rules parallel to legacy logic to compare results and ensure a smooth transition without downtime).

Installation

Rust

Add to your Cargo.toml:

[dependencies]
fast-decision = "0.2.4"

Python

pip install fast-decision

Or install from source:

git clone https://github.com/almayce/fast-decision.git
cd fast-decision
maturin develop --release

Quick Start

Rust Example

use fast_decision::{RuleEngine, RuleSet};
use serde_json::json;

fn main() {
    let rules_json = r#"
    {
      "categories": {
        "Pricing": {
          "stop_on_first": true,
          "rules": [
            {
              "id": "Platinum_Discount",
              "priority": 1,
              "conditions": {"user.tier": {"$equals": "Platinum"}},
              "action": "apply_20_percent_discount"
            },
            {
              "id": "Gold_Discount",
              "priority": 10,
              "conditions": {"user.tier": {"$equals": "Gold"}},
              "action": "apply_10_percent_discount"
            }
          ]
        }
      }
    }
    "#;

    let ruleset: RuleSet = serde_json::from_str(rules_json).unwrap();
    let engine = RuleEngine::new(ruleset);

    let data = json!({
        "user": {"tier": "Gold", "id": 123},
        "transaction": {"amount": 100}
    });

    let results = engine.evaluate_rules(&data, &["Pricing"]);
    println!("Triggered rules: {:?}", results);
    // Output: ["Gold_Discount"]
}

Python Example

See python/README.md for detailed Python documentation.

from fast_decision import FastDecision

# Load rules from JSON file
engine = FastDecision("rules.json")

# Evaluate rules
data = {
    "user": {"tier": "Gold", "id": 123},
    "transaction": {"amount": 100}
}

results = engine.evaluate_rules(data, categories=["Pricing"])
print(f"Triggered rules: {results}")
# Output: ['Gold_Discount']

Rule Format

Rules are defined in JSON:

{
  "categories": {
    "CategoryName": {
      "stop_on_first": true,
      "rules": [
        {
          "id": "rule_identifier",
          "priority": 1,
          "conditions": {
            "field.path": {"$equals": "value"}
          },
          "action": "action_name",
          "metadata": {
            "source": "Pricing Rules v2.3",
            "tags": ["discount", "promotion"],
            "description": "Optional custom data for tracking"
          }
        }
      ]
    }
  }
}

Rule Fields

• id (required): Unique rule identifier
• priority (required): Evaluation priority (lower = higher precedence)
• conditions (required): Condition tree for evaluation
• action (required): Action identifier (informational, not evaluated by engine)
• metadata (optional): Custom metadata for tracing, compliance, or annotations. Will be included in evaluation results if present.

Supported Operators

Comparison Operators

Operator	Description	Example
$equals	Equal	{"age": {"$equals": 18}}
$not-equals	Not equal	{"status": {"$not-equals": "inactive"}}
$greater-than	Greater than	{"score": {"$greater-than": 100}}
$less-than	Less than	{"price": {"$less-than": 50}}
$greater-than-or-equals	Greater than or equal	{"age": {"$greater-than-or-equals": 21}}
$less-than-or-equals	Less than or equal	{"count": {"$less-than-or-equals": 10}}

Membership Operators

Operator	Description	Example
$in	Value in array	{"tier": {"$in": ["Gold", "Platinum"]}}
$not-in	Value not in array	{"status": {"$not-in": ["banned", "suspended"]}}

String Operators

Operator	Description	Example
$contains	Case-sensitive substring	{"description": {"$contains": "premium"}}
$starts-with	String starts with	{"name": {"$starts-with": "Dr."}}
$ends-with	String ends with	{"email": {"$ends-with": "@company.com"}}
$regex	Regular expression	{"email": {"$regex": "^[a-z]+@[a-z]+\\.[a-z]+$"}}

Logical Operators

Implicit AND - Multiple conditions in one object:

{
  "conditions": {
    "age": {"$greater-than-or-equals": 18, "$less-than": 65},
    "status": {"$equals": "active"}
  }
}

Explicit OR - Use $or:

{
  "conditions": {
    "$or": [
      {"tier": {"$equals": "Platinum"}},
      {"score": {"$greater-than": 1000}}
    ]
  }
}

Nested Logic:

{
  "conditions": {
    "$or": [
      {"tier": {"$equals": "Platinum"}},
      {
        "tier": {"$equals": "Gold"},
        "amount": {"$greater-than": 500}
      }
    ]
  }
}

Performance

Benchmarks

Run benchmarks:

cargo bench

Optimization Features

• Rust backend: Native machine code performance
• Zero allocations in hot evaluation path
• Inline functions: Critical comparison functions marked #[inline(always)]
• Optimized data structures: Box<[String]> for path tokens, #[repr(u8)] for operators
• Pre-sorted rules: Rules sorted by priority at load time
• Direct conversion: Python dict → Rust without intermediate JSON serialization
• Link Time Optimization (LTO): Enabled in release profile

Performance Characteristics

• Rule evaluation: O(n) where n = number of rules in requested categories
• Field lookup: O(d) where d = depth of nested field path
• Memory: Minimal allocations during evaluation (only for results)

Development

# Run tests
cargo test

# Run Rust examples
cargo run --example demo

# Build documentation
cargo doc --no-deps --open

# Run Python tests
cd python/tests
python test_features.py

Contributing

See CONTRIBUTING.md for development guidelines.

Architecture

fast-decision/
├── src/              # Rust core engine
│   ├── lib.rs        # Python bindings (PyO3)
│   ├── engine.rs     # Rule evaluation engine
│   └── types.rs      # Data structures
├── benches/          # Performance benchmarks
├── examples/         # Rust examples
├── python/           # Python bindings and examples
│   ├── examples/     # Usage examples
│   └── tests/        # Tests
├── Cargo.toml        # Rust configuration
└── pyproject.toml    # Python packaging

License

Licensed under either of:

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.