Cache-Aside Generator

Creates Cache-Aside infrastructure with stampede protection and tag-based invalidation.

When to Use

Scenario	Example
Read-heavy workloads	Product catalog, user profiles
Expensive queries	Complex reports, aggregated data
External API responses	Third-party API caching
Computed values	Pricing calculations, search results

Component Characteristics

CacheAsideInterface

• get(string $key, callable $loader, int $ttl): mixed — load from cache or compute
• invalidate(string $key): void — remove specific cache entry
• invalidateByTag(string $tag): void — remove all entries tagged with given tag

CacheKeyGenerator

• Builds deterministic cache keys from prefix and parameters
• Hashes long keys to prevent exceeding storage limits
• Supports tag-based key grouping

CacheAsideExecutor

• PSR-16 SimpleCache integration
• Configurable TTL per cache operation
• Stampede protection via distributed locking
• Prevents thundering herd on cache miss

CacheInvalidator

• Tag-based invalidation (invalidate all entries for a tag)
• Pattern-based clearing (wildcard key matching)
• Batch invalidation support

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Generation Process

Step 1: Generate Domain Components

Path: src/Domain/Shared/Cache/

1. CacheAsideInterface.php — Cache-aside contract
2. CacheKeyGeneratorInterface.php — Key generation contract

Step 2: Generate Infrastructure Components

Path: src/Infrastructure/Cache/

1. CacheKeyGenerator.php — Key builder with hashing
2. CacheAsideExecutor.php — PSR-16 cache executor with locking
3. CacheInvalidator.php — Tag-based and pattern-based invalidation
4. CacheLockInterface.php — Distributed lock contract
5. RedisCacheLock.php — Redis-based lock implementation

Step 3: Generate Tests

1. CacheKeyGeneratorTest.php — Key generation and hashing tests
2. CacheAsideExecutorTest.php — Cache hit/miss, stampede protection tests
3. CacheInvalidatorTest.php — Tag and pattern invalidation tests

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File Placement

Component	Path
Domain Interfaces	src/Domain/Shared/Cache/
Infrastructure	src/Infrastructure/Cache/
Unit Tests	tests/Unit/Infrastructure/Cache/

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Naming Conventions

Component	Pattern	Example
Interface	CacheAsideInterface	CacheAsideInterface
Key Generator	CacheKeyGenerator	CacheKeyGenerator
Executor	CacheAsideExecutor	CacheAsideExecutor
Invalidator	CacheInvalidator	CacheInvalidator
Lock Interface	CacheLockInterface	CacheLockInterface
Lock Impl	{Store}CacheLock	RedisCacheLock
Test	{ClassName}Test	CacheAsideExecutorTest

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Quick Template Reference

CacheAsideInterface

interface CacheAsideInterface
{
    /**
     * @template T
     * @param callable(): T $loader
     * @return T
     */
    public function get(string $key, callable $loader, int $ttl = 3600): mixed;
    public function invalidate(string $key): void;
    public function invalidateByTag(string $tag): void;
}

CacheKeyGenerator

final readonly class CacheKeyGenerator
{
    public function __construct(private string $prefix = 'app');
    public function generate(string $context, string ...$parts): string;
    public function generateHashed(string $context, string ...$parts): string;
}

CacheLockInterface

interface CacheLockInterface
{
    public function acquire(string $key, int $ttl = 10): bool;
    public function release(string $key): void;
}

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Usage Example

$executor = new CacheAsideExecutor($cache, $lock, defaultTtl: 3600);

// Cache-aside: returns cached value or computes via loader
$product = $executor->get(
    key: 'product:123',
    loader: fn() => $repository->findById(123),
    ttl: 1800
);

// Invalidate on update
$executor->invalidate('product:123');

// Tag-based invalidation
$invalidator->invalidateByTag('products');

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Pattern Comparison

Pattern	Description	Use Case
Cache-Aside	App manages cache (check → miss → load → store)	Read-heavy, tolerates stale data
Read-Through	Cache loads data on miss (transparent to app)	Simpler app code, cache manages loading
Write-Through	Write to cache and DB simultaneously	Strong consistency needed
Write-Behind	Write to cache, async write to DB	High write throughput, eventual consistency

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Anti-patterns to Avoid

Anti-pattern	Problem	Solution
No TTL	Stale data served forever	Always set TTL, even long ones
Thundering herd	All requests compute on cache miss	Stampede protection with locking
Cache poisoning	Invalid data cached	Validate data before caching
Inconsistent invalidation	Update DB but forget cache	Use events/listeners for invalidation
Key collisions	Different data for same key	Use prefix + context + params
Over-caching	Memory waste, stale data	Cache only expensive/frequent operations

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References

For complete PHP templates and examples, see:

• references/templates.md — CacheAsideInterface, CacheKeyGenerator, CacheAsideExecutor, CacheInvalidator, lock templates
• references/examples.md — Repository integration, event-driven invalidation, and unit tests