> ## Documentation Index
> Fetch the complete documentation index at: https://docs.pillar8.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Architecture

Pillar8 operates as a decision layer positioned before payment execution. It sits between the merchant checkout and the existing payment stack, generating a decision package for each checkout session.

## System Flow

```text theme={null}
Shopper → Merchant Checkout → Pillar8 Decision Engine → Orchestrator / PSPs → Issuer
```

## Core Capabilities

<Columns cols={2}>
  <Card title="What Pillar8 Does" icon="check">
    * Captures checkout context
    * Evaluates transaction patterns
    * Generates a decision package
    * Influences checkout behavior
  </Card>

  <Card title="What Pillar8 Does Not Do" icon="x">
    * Process payments
    * Replace PSPs
    * Replace orchestration
    * Route transactions directly
    * Modify payment infrastructure
  </Card>
</Columns>

## Decision Package

For each session, Pillar8 returns:

* **Ranked payment methods** — Ordered by relevance and success likelihood
* **Contextual scoring signals** — Transaction pattern evaluation
* **Confidence indicators** — Decision certainty metrics
* **Gating and eligibility logic** — Access controls and rules

The package can be applied by different execution surfaces depending on the checkout environment.

## Execution Surfaces

<AccordionGroup>
  <Accordion title="Advisory layer" icon="lightbulb">
    Pillar8 guides shoppers through an advisory block displayed in checkout.
  </Accordion>

  <Accordion title="Merchant-controlled execution" icon="sliders">
    Merchants can apply the decision package by:

    * Highlighting payment options
    * Reordering methods
    * Shaping checkout behavior
  </Accordion>

  <Accordion title="Insights layer" icon="chart-line">
    Decisions and outcomes are captured and surfaced in the merchant portal for analysis.
  </Accordion>
</AccordionGroup>

## Platform Dependency

How the decision package is applied depends on the merchant's environment and checkout control. Some platforms support guidance only, while others allow deeper checkout execution.