SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ca569a68cb232f4434c32026704f3785545e365fc7068f758753fe1c59db3fd' 
  AND token = 'JgbUE/2PzGbHQG8OlEI/AJNBhjyi/Eo+FG8BqDVJGjg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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