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

# Memory & Keychain

> PrismMemoryStore LRU cache with statistics and PrismKeychainStore for secure credential storage

## PrismMemoryStore

Actor-based in-memory LRU cache with per-entry TTL, automatic eviction, and hit/miss statistics.

```swift theme={null}
let cache = PrismMemoryStore(
    maxEntries: 1000,
    defaultTTL: 600 // 10 min
)

// Standard CRUD
try await cache.save(user, forKey: "user-42")
let user = try await cache.load(User.self, forKey: "user-42")

// Per-entry TTL
try await cache.save(otp, forKey: "otp", ttl: 30) // 30 sec
```

### LRU Eviction

When `maxEntries` is exceeded, least-recently-accessed entries are evicted first. Access (load) refreshes an entry's position.

### Statistics

```swift theme={null}
let stats = await cache.statistics()
print("Hit rate: \(stats.hitRate)")  // 0.0–1.0
print("Hits: \(stats.hits)")
print("Misses: \(stats.misses)")
print("Evictions: \(stats.evictions)")
print("Expirations: \(stats.expirations)")

let count = await cache.count()
```

## PrismKeychainStore

Secure credential storage using the Security framework (SecItem APIs). Conforms to `PrismStorageProtocol`.

```swift theme={null}
let keychain = PrismKeychainStore(
    service: "com.myapp.auth",
    accessGroup: "TEAM.com.myapp.shared" // optional
)

// Store credentials
try keychain.save("Bearer abc123", forKey: "accessToken")
try keychain.save(credentials, forKey: "oauth") // any Codable

// Retrieve
let token = try keychain.load(String.self, forKey: "accessToken")

// Check existence
if try keychain.exists(forKey: "accessToken") { ... }

// Remove
try keychain.delete(forKey: "accessToken")
try keychain.clear() // remove all items for this service
```

### Security Notes

* Data stored via `kSecClassGenericPassword`
* Scoped by `service` identifier
* `accessGroup` enables Keychain Sharing across apps
* `keys()` uses `kSecMatchLimitAll` + `kSecReturnAttributes`
* Thread-safe via `NSLock`