Clojurians Log v2

using an iterator instead of a lazy-seq and doing a channel op for each element is less complex than using a lazy-seq IMHO, lazy-seq is a data abstraction and not conducive to doing IO or compute tasks

Sounds like you don't need core.async at all and instead just want a primitive for limiting max number of concurrent calls. As mentioned above, claypoole might be a useful thing to look at. I use something like this: https://github.com/jumarko/clojure-experiments/blob/master/src/clojure_experiments/concurrency.clj#L62-L74

(defn re-chunk [n xs]
  (lazy-seq
   (when-let [s (seq (take n xs))]
     (let [cb (chunk-buffer n)]
       (doseq [x s] (chunk-append cb x))
       (chunk-cons (chunk cb) (re-chunk n (drop n xs)))))))

(defn map-throttled
  "Like `map` but never realizes more than `max-n` elements ahead of the consumer of the return value.
  Useful for cases like an rate limited asynchronous HTTP API (e.g. StartQuery AWS CloudWatch Insights API).
  Uses `re-chunk`."
  [max-n f coll]
  (map f (re-chunk max-n coll)))