Memory Extended Cache Driver

The Memory Extended Cache Driver is similar to the Memory Cache Driver, but with sliding expiration: every time you access a key, its TTL is reset.

When to Use

• You want cache entries to stay alive as long as they're being used
• Session-like or frequently accessed data

Best For

• User sessions
• Frequently accessed, but not permanent, data

Limitations

• Data is lost on restart
• Not shared between processes or servers
• No eviction policy (see LRU Memory Cache Driver)

Configuration

src/config/cache.ts

import { MemoryExtendedCacheDriver } from "@warlock.js/cache";

const cacheConfigurations = {
  drivers: {
    memoryExtended: MemoryExtendedCacheDriver,
  },
  default: "memoryExtended",
  options: {
    memoryExtended: {
      globalPrefix: "sessions",
      ttl: 600, // 10 minutes
    },
  },
};

Options

Option	Type	Default	Description
globalPrefix	string | Function	undefined	Global prefix for all cache keys
ttl	number	Infinity	Default TTL in seconds

Global Prefix

{
  globalPrefix: "sessions",    // Static prefix
  // OR
  globalPrefix: () => `app-${environment()}`, // Dynamic prefix
}

TTL Configuration

{
  ttl: 600,                    // 10 minutes
  // OR
  ttl: 3600,                   // 1 hour
  // OR
  ttl: Infinity,               // Never expire (default)
}

Example Usage

Storing and Retrieving Data

import { cache } from "@warlock.js/cache";

await cache.set("session.abc", { userId: 1 }, CACHE_FOR.HALF_HOUR);
const session = await cache.get("session.abc"); // TTL resets to 30 minutes

Sliding Expiration Explained

Unlike the regular Memory Cache Driver, the Memory Extended Driver implements sliding expiration:

1. Initial Set: When you set a value with TTL, it's stored with an expiration time
2. Access Resets TTL: Every time you access the value, the TTL is reset to the original duration
3. Continuous Access: As long as the value is accessed within the TTL window, it never expires
4. Inactivity Expiration: Only when the value is not accessed for the full TTL duration does it expire

Example Timeline

import { cache, CACHE_FOR } from "@warlock.js/cache";

// TTL: 30 minutes
await cache.set("session.123", data, CACHE_FOR.HALF_HOUR);

// After 15 minutes
await cache.get("session.123"); // TTL resets to 30 minutes

// After another 20 minutes (35 minutes total)
await cache.get("session.123"); // TTL resets to 30 minutes again

// If not accessed for 30 minutes, it expires

Use Cases

• User Sessions: Keep sessions alive as long as users are active
• API Rate Limiting: Reset counters on each request
• Frequently Accessed Data: Keep hot data in cache longer
• Temporary State: Maintain state that should persist during activity

Troubleshooting

• Data disappears after restart: This is expected. Use File or Redis for persistence.
• Cache not shared between processes: Use Redis for distributed cache.
• Items expiring too quickly: Increase the ttl value or access them more frequently.