ETag (Entity Tag)
An ETag, or entity tag, is an HTTP response header containing a version identifier for a resource. Clients send it back in an If-None-Match header, and if the resource has not changed, the server replies with 304 Not Modified and no body, saving bandwidth.
Technical Architecture & Deep-Dive
ETags are usually a hash of the response content. A mobile app that cached a large configuration payload can revalidate it cheaply: the request carries the stored ETag, and an unchanged resource returns only headers.
Edge gateways can generate ETags for composed or slimmed responses, giving clients conditional request support even when the underlying upstream APIs do not provide it.
Key Architectural Benefits
Implement ETag (Entity Tag) at the Edge
Deploy lightweight API aggregation, edge caching, and secret injection in minutes without Docker containers or complex servers.
Frequently Asked Questions
Q:What is the difference between strong and weak ETags?
Strong ETags indicate byte-for-byte identical content. Weak ETags, prefixed with W/, indicate semantically equivalent content that may differ in bytes.
Related Architecture Concepts
Cache-Control is an HTTP response header that tells browsers, CDNs, and proxies whether and how long a response may be cached. Directives such as max-age, s-maxage, private, no-store, and stale-while-revalidate control freshness and sharing for every cached copy.
API bandwidth optimization is reducing the amount of data transferred between APIs and clients. Techniques include removing unused fields, compressing responses, caching close to users, using conditional requests, and aggregating calls to avoid redundant transfers.
Edge Caching is the practice of storing computed API responses on globally distributed Point of Presence (PoP) servers situated geographically close to users. By serving cached responses directly from edge memory, requests achieve sub-10ms latencies while offloading 95%+ of traffic from origin databases.