# Solution Architecture Document

## Meter Read Integration — AMI Head-End to SAP IS-U

| Field | Value |
| --- | --- |
| Document ID | EAOT-SAD-001 |
| Version | 1.0 |
| Status | Approved |
| Classification | Internal |
| Author | Enterprise Architecture Office |

---

## 1. Purpose

This document describes the solution architecture for integrating the AMI
(Advanced Metering Infrastructure) head-end system with SAP IS-U for
interval meter-read ingestion, validation, and billing determination.

## 2. Scope

**In scope**
- Scheduled and on-demand interval meter read collection
- Read validation, estimation, and editing hand-off (VEE)
- Delivery of billing-ready register and interval reads to SAP IS-U
- Operational alerting and replay of failed messages

**Out of scope**
- Meter firmware management
- Customer-facing usage portal
- Head-end collection network (RF mesh) design

## 3. Architecture Overview

```text
[Smart Meters] --RF mesh--> [AMI Head-End] --events--> [Kafka Backbone]
                                                              |
                                        +---------------------+-------------------+
                                        |                                         |
                                 [Read Validator]                              [Replay Store]
                                        |
                                 [Integration Layer (API-led)]
                                        |
                                  [SAP IS-U]
```

## 4. Key Design Decisions

| ID | Decision | Rationale |
| --- | --- | --- |
| AD-01 | Event-driven backbone (Kafka) | Decouples 1M+ daily reads from IS-U throughput limits |
| AD-02 | API-led experience layer | Reuse across billing, analytics, and portal channels |
| AD-03 | Idempotent consumers with read-ID keys | Exactly-once effect across replay windows |

## 5. Non-Functional Requirements

| Category | Requirement | Target |
| --- | --- | --- |
| Throughput | Peak interval reads | 12,000 msg/min |
| Latency | Read to IS-U availability | < 15 min (P95) |
| Availability | Integration layer | 99.9% |
| Security | In transit / at rest | TLS 1.3, AES-256 |
| Auditability | Replay window | 30 days |

## 6. Security

- mTLS between head-end collector and backbone
- OAuth2 client-credentials for IS-U BAPI wrapper APIs
- Schema registry enforces Avro contracts; PII tagged and masked downstream

## 7. Error Handling & Monitoring

- Dead-letter topics per domain with 3-attempt exponential backoff
- Prometheus metrics: lag, DLQ rate, read-to-billing latency
- Alerting thresholds: DLQ rate > 0.1%, lag > 5 min

## 8. Deployment

- Containerised consumers on Kubernetes; horizontal autoscaling on lag
- Blue/green releases via GitHub Actions pipeline

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