SiftingIO’s tutorial on market data API caching starts from a watchlist: “Two hundred people opening the same watchlist do not necessarily need two hundred requests for the same price.” Its demonstration is three waves of 200 callers at 0, 500 and 1,000 milliseconds against a one-second TTL. With no cache, 600 upstream calls. With a TTL cache and no coalescing, 400, because every wave that finds an expired entry stampedes. With TTL plus request coalescing, where simultaneous misses share one in-flight fetch, two. The post ships the Node.js helper that does it, bounded to a server-configured set of keys. Its most useful distinction is a timestamp one: a price stamped 12:00:00, received at 12:00:08 and served at 12:00:08.4 has a cache age of 0.4 seconds and a data age of 8.4 seconds. “Cache age tells you when you fetched a response. It does not tell you when its price was produced.”
There is a vendor figure here and the vendor discounts it before anyone else can. The 600, 400 and 2 are “counts from a controlled example, not a production savings forecast,” the one-second TTL is “an example setting, not a claim about a provider’s update rate,” and the code was tested with synthetic values and a fixed clock. The pitch is a SiftingIO account and the Forex API, named in the first paragraph and the last. What survives is all of it, because the post never claims more than it shows: build keys from scope, product, instrument, parameters and response version, never from the API secret; authorize before every cache lookup; return Cache-Control no-store on authenticated quote routes; and remember that “caching is an engineering choice, not permission to redistribute data.”
The catalog confirms the surface the tutorial caches. SiftingIO on apis.io carries 13 API pages. The snapshot being cached is the SiftingIO Forex API and the SiftingIO Live API. The post’s advice that a display needing every update should move to “a server-side stream rather than lengthening a snapshot cache” points at the SiftingIO Live Stream, described in the catalog by a public AsyncAPI 3.0 contract. The session-aware freshness policy and market calendar the helper deliberately does not implement are what the SiftingIO Markets API covers, market status, hours and holidays. The catalog record lists 37 operations under an OpenAPI 3.1 contract, a FIX 4.4 feed, Go, Python and JavaScript SDKs and an open-source MCP server with 36 tools, and the agentic access profile counts the same 37.
SiftingIO scores 65.1 on the Kin Score, strong. Access clarity is 84.2, developer ergonomics 83.3 and operational transparency 76.3, the profile of a provider that writes tutorials like this one. Agent Readiness is 37.6, agent-ready, with error semantics, OpenAPI examples, event surface, agent skills, rate limit signal and MCP server all lit. The hole is contract governance at 4.5, the lowest facet by a wide margin. That lands on the one slot in the post’s own cache key it cannot fill from the provider’s side. The guide tells you to include the response version in every key and to revalidate historical bars against a dataset version. The contract behind those keys declares almost nothing about how it versions, deprecates or changes. The cache is engineered to notice a version change the provider has not yet promised to announce.