Cache Patterns Explained: Choose the Right Strategy for Your App

Cache-Aside

Cache-Aside is the most common caching pattern where the application controls all interactions with both the cache and the database. The cache does not communicate directly with the database.

Read Process

The application checks if the data exists in the cache.

If the cache hits, the data is returned directly from the cache.

If the cache misses, the application reads the data from the database, stores it in the cache, and then returns it.

Write Strategies

Two write strategies are discussed.

First Strategy (Update DB then Cache)

Update the database first, then update the cache. This can cause thread‑safety issues, leading to stale (dirty) data in the cache when multiple write threads interleave.

Second Strategy (Update DB then Delete Cache)

Update the database, then delete the corresponding cache entry. This avoids dirty data but may still have rare race conditions; however, the likelihood is low.

Application Scenario

Used when the caching system does not support Read‑Through/Write‑Through.

Advantages

Lazy loading: only requested data is cached, reducing unnecessary cache updates.

Disadvantages

Cache miss incurs extra latency due to database read and cache write.

Complex logic duplicated across services in microservice architectures.

Read-Through/Write-Through

In this model, the cache acts as the primary data source; the database is transparent to the application. The cache handles both reads and writes on behalf of the application.

Read-Through

The cache is configured with a read module that knows how to load data from the database into the cache on a miss.

Write-Through

The cache writes data to both the cache and the database synchronously, ensuring data consistency.

Application Scenario

Suitable for applications where written data is frequently read.

Advantages

No dirty data in the cache.

Higher read speed compared to lazy‑loading patterns.

Simpler application logic.

Disadvantages

Performance waste for write‑heavy, read‑light workloads.

Write-Back

Also known as Write-Behind. Writes are performed to the cache first, and the database is updated asynchronously, e.g., when the cache entry is evicted or in batch.

Application Scenario

Ideal for read‑write intensive applications where fast writes are needed.

Advantages

Very fast read and write operations because they interact directly with the cache.

Provides tolerance for temporary database outages.

Disadvantages

Risk of data loss if the cache fails before data is persisted to the database.

Write-Around

Unlike Write‑Through, updates are written only to the database, not the cache. Used together with Read‑Through or Cache‑Aside, the cache is updated only on a miss.

Application Scenario

Best for data that is written once and rarely read.

Advantages

Higher write efficiency when data is seldom read, avoiding unnecessary cache population.

Disadvantages

Potential inconsistency if data is written multiple times.