SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8be84b98c2d6582280c6eac6a2f91eab913eeb787e1d95b317688328a8aa9cba' 
  AND token = '8udPtxBK3doPywWv8AwDD0l6bIMMh+fN+uzdvkfMlKs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}