# Cache & Performance (Symfony)

> Cache pools, adapters, tags, cache invalidation, HTTP cache, ESI, Varnish integration

- 20 interview questions
- Mid-Level
- [Interview Questions: Symfony](https://sharpskill.dev/en/technologies/symfony/interview-questions.md)

## 1. Which interface does Symfony use to implement the PSR-6 cache system?

**Answer**

Symfony implements the PSR-6 standard through the CacheItemPoolInterface. This interface defines methods getItem(), hasItem(), deleteItem(), save() and clear() for managing cache items. Symfony's Cache component provides several adapters (Redis, Memcached, Filesystem, etc.) that all implement this interface, ensuring interoperability with other PSR-6 compatible PHP libraries.

## 2. What is the default cache adapter configured in Symfony for the development environment?

**Answer**

In development environment, Symfony uses the ArrayAdapter by default which stores cache in memory. This cache is not persistent between requests, which is ideal for development as it avoids stale cache issues when modifying code. In production, it is recommended to use a persistent adapter like Redis or Memcached for better performance.

## 3. How to create a custom cache pool in Symfony configuration?

**Answer**

Custom cache pools are defined under the framework.cache.pools key in configuration. Each pool can specify its adapter, default lifetime (default_lifetime), and optionally tags. For example, a 'app.cache.products' pool with RedisAdapter allows managing product cache independently from other data, facilitating targeted invalidation.

## 17 more questions available

- Which method to use to retrieve a value from cache with a computation callback if missing?
- What is the main advantage of cache tags in Symfony?

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## Other Symfony interview topics

- [Modern PHP (8.1+)](https://sharpskill.dev/en/technologies/symfony/interview-questions/php-modern-features.md): 20 questions, Junior
- [Symfony Basics](https://sharpskill.dev/en/technologies/symfony/interview-questions/symfony-basics.md): 25 questions, Junior
- [Routing & Controllers](https://sharpskill.dev/en/technologies/symfony/interview-questions/routing-controllers.md): 20 questions, Junior
- [Twig & Templates](https://sharpskill.dev/en/technologies/symfony/interview-questions/twig-templates.md): 20 questions, Junior
- [Doctrine ORM Basics](https://sharpskill.dev/en/technologies/symfony/interview-questions/doctrine-orm-basics.md): 25 questions, Junior
- [Symfony Forms](https://sharpskill.dev/en/technologies/symfony/interview-questions/forms.md): 22 questions, Junior
- [Data Validation](https://sharpskill.dev/en/technologies/symfony/interview-questions/validation.md): 18 questions, Junior
- [Dependency Injection & Services](https://sharpskill.dev/en/technologies/symfony/interview-questions/dependency-injection.md): 24 questions, Mid-Level
- [Security & Authentication](https://sharpskill.dev/en/technologies/symfony/interview-questions/security-authentication.md): 26 questions, Mid-Level
- [Doctrine Advanced](https://sharpskill.dev/en/technologies/symfony/interview-questions/doctrine-advanced.md): 24 questions, Mid-Level
- [API Platform](https://sharpskill.dev/en/technologies/symfony/interview-questions/api-platform.md): 22 questions, Mid-Level
- [Serializer Component](https://sharpskill.dev/en/technologies/symfony/interview-questions/serializer.md): 20 questions, Mid-Level
- [Events & Event Subscribers](https://sharpskill.dev/en/technologies/symfony/interview-questions/events-subscribers.md): 20 questions, Mid-Level
- [Console & Commands](https://sharpskill.dev/en/technologies/symfony/interview-questions/console-commands.md): 18 questions, Mid-Level
- [Messenger Component](https://sharpskill.dev/en/technologies/symfony/interview-questions/messenger.md): 22 questions, Mid-Level
- [HTTP Client](https://sharpskill.dev/en/technologies/symfony/interview-questions/http-client.md): 18 questions, Mid-Level
- [Workflow Component](https://sharpskill.dev/en/technologies/symfony/interview-questions/workflow.md): 18 questions, Mid-Level
- [Testing Symfony](https://sharpskill.dev/en/technologies/symfony/interview-questions/testing.md): 22 questions, Mid-Level
- [Mailer Component](https://sharpskill.dev/en/technologies/symfony/interview-questions/mailer.md): 16 questions, Mid-Level
- [Translations & i18n](https://sharpskill.dev/en/technologies/symfony/interview-questions/translations.md): 16 questions, Mid-Level
- [EasyAdmin Bundle](https://sharpskill.dev/en/technologies/symfony/interview-questions/easyadmin.md): 18 questions, Mid-Level
- [Symfony Architecture](https://sharpskill.dev/en/technologies/symfony/interview-questions/architecture-patterns.md): 24 questions, Senior
- [Performance & Optimization](https://sharpskill.dev/en/technologies/symfony/interview-questions/performance-optimization.md): 22 questions, Senior
- [Security Advanced](https://sharpskill.dev/en/technologies/symfony/interview-questions/security-advanced.md): 22 questions, Senior
- [Custom Bundles](https://sharpskill.dev/en/technologies/symfony/interview-questions/custom-bundles.md): 20 questions, Senior
- [Microservices with Symfony](https://sharpskill.dev/en/technologies/symfony/interview-questions/microservices.md): 22 questions, Senior
- [Real-time & WebSockets](https://sharpskill.dev/en/technologies/symfony/interview-questions/real-time.md): 18 questions, Senior
- [Deployment & DevOps](https://sharpskill.dev/en/technologies/symfony/interview-questions/deployment-devops.md): 20 questions, Senior

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