axiom-storage

# iOS Storage Guide

**Purpose**: Navigation hub for ALL storage decisions — database vs files, local vs cloud, specific locations
**iOS Version**: iOS 17+ (iOS 26+ for latest features)
**Context**: Complete storage decision framework integrating SwiftData (WWDC 2023), CKSyncEngine (WWDC 2023), and file management best practices

## When to Use This Skill

✅ **Use this skill when**:
- Starting a new project and choosing storage approach
- Asking "where should I store this data?"
- Deciding between SwiftData, Core Data, SQLite, or files
- Choosing between CloudKit and iCloud Drive for sync
- Determining Documents vs Caches vs Application Support
- Planning data architecture for offline/online scenarios
- Migrating from one storage solution to another
- Debugging "files disappeared" or "data not syncing"

❌ **Do NOT use this skill for**:
- SwiftData implementation details (use `axiom-swiftdata` skill)
- SQLite/GRDB specifics (use `axiom-sqlitedata` or `axiom-grdb` skills)
- CloudKit sync implementation (use `axiom-cloudkit-ref` skill)
- File protection APIs (use `axiom-file-protection-ref` skill)

**Related Skills**:
- Existing database skills: `axiom-swiftdata`, `axiom-sqlitedata`, `axiom-grdb`
- New file skills: `axiom-file-protection-ref`, `axiom-storage-management-ref`, `axiom-storage-diag`
- New cloud skills: `axiom-cloudkit-ref`, `axiom-icloud-drive-ref`, `axiom-cloud-sync-diag`

## Core Philosophy

> **"Choose the right tool for your data shape. Then choose the right location."**

Storage decisions have two dimensions:
1. **Format**: How is data structured? (Queryable records vs files)
2. **Location**: Where is it stored? (Local vs cloud, which directory)

Getting the format wrong forces workarounds. Getting the location wrong causes data loss or backup bloat.

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## The Complete Decision Tree

### Level 1: Format — What Are You Storing?

```
What is the shape of your data?

├─ STRUCTURED DATA (queryable records, relationships, search)
│   Examples: User prof