Amazon ElastiCache vs Varnish Cache

Amazon ElastiCache is a managed caching service compatible with Valkey, Memcached, and Redis OSS, with performance described as microsecond latency. Customers can deploy a serverless cache or a node-based cluster. ElastiCache Serverless monitors compute, memory, and network use and scales vertically and horizontally as demand changes. It replicates data across multiple Availability Zones and offers a 99.99% availability SLA for each cache. Listed uses include application and semantic caching, data and session stores, and leaderboards. It can act as a front-end cache for Amazon RDS, Aurora, DocumentDB, and DynamoDB, and improve performance with EC2 and EMR. Security options include encryption in transit and at rest, IAM authentication, Valkey or Redis OSS AUTH, and role-based access control. CloudWatch provides more than 40 operational metrics at no additional charge. Valkey serverless pricing starts at $6 a month, billed according to stored data in GB-hours and requests measured in ECPUs. Data tiering is unavailable with ElastiCache Serverless.

Varnish Cache is a reverse caching proxy for Linux and self-hosted deployments. It serves cached responses from memory and sends other requests to origin servers. Its caching policy is defined in Varnish Configuration Language (VCL), which compiles to native code. Cached objects follow standard HTTP cache headers and leave the cache when they expire. Varnish supports TLS termination within the process and TLS connections to dynamic origin backends. It includes varnishlog for structured logging and varnishstat for metrics, and offers official container images and a Kubernetes Helm chart. Installation guidance covers Debian, Ubuntu, Red Hat Enterprise Linux, and compatible distributions. Varnish modules add functions callable from VCL. Its security guide describes controls at the command-line, CLI, VCL, and HTTP request levels. The free plan costs nothing. One limit to account for: Varnish avoids caching data when it cannot determine that doing so is safe, and applications may need configuration changes to reach a high cache hit rate.