Handlebars.compile concurrency safety and caching configuration

The goal is to guarantee that each Handlebars template is compiled only once when multiple requests arrive simultaneously, preventing redundant synchronous compile work that blocks the Node.js event loop and creates latency spikes. Handlebars.compile is a synchronous function; while it stores results in Handlebars.templates by name, the library provides no internal locking or deduplication mechanism for concurrent calls to the same template name.

Because the API does not expose a built‑in thread‑safe cache, developers must decide whether to rely on external memoization, pre‑compilation, or another strategy to achieve single‑compile behavior under load. The uncertainty lies in what configuration or pattern, if any, can be adopted without introducing external dependencies while still respecting the library’s current design.

What configuration options exist to enable automatic deduplication of Handlebars.compile calls under concurrent requests?
Is there a supported way to make Handlebars.template lookup atomic without external caching?
Should applications treat Handlebars.compile as inherently unsafe for hot paths unless wrapped in a user‑provided cache?