SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21a58bbfc560ea9bc35b57f37eaa3d1b4db1dd7caf6bfcf549b60547d2baf3f3' 
  AND token = 'EpWWuRneRL6KtqhF13Cr6BHWzUGmoGs23o8WDMYqbLA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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