# Module: Azaion.Services.Cache

## Purpose
In-memory caching abstraction using LazyCache, providing get-or-add and invalidation operations.

## Public Interface

### ICache
| Method | Signature | Description |
|--------|-----------|-------------|
| `GetFromCacheAsync<T>` | `Task<T> GetFromCacheAsync<T>(string key, Func<Task<T>> fetchFunc, TimeSpan? expiration = null)` | Returns cached value or fetches and caches it |
| `Invalidate` | `void Invalidate(string key)` | Removes a key from the cache |

### MemoryCache (implementation)
Default expiration: 4 hours (`TimeSpan.FromHours(4)`).

## Internal Logic
Wraps `LazyCache.CachingService`. `GetFromCacheAsync` uses `GetOrAddAsync` with absolute expiration relative to now. `Invalidate` calls `Remove`.

## Dependencies
- LazyCache (`IAppCache`, `CachingService`)

## Consumers
- `UserService.GetByEmail` — caches user lookups by `User.GetCacheKey(email)`
- `UserService.UpdateHardware`, `UserService.UpdateQueueOffsets`, `UserService.CheckHardwareHash` — invalidate cache after writes
- Registered as `Scoped` in DI (`Program.cs`): `AddScoped<ICache, MemoryCache>`

## Data Models
None.

## Configuration
None — default 4-hour expiration is hardcoded.

## External Integrations
None.

## Security
None.

## Tests
`MemoryCache` is instantiated directly in `UserServiceTest`.