SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a5192c20db78b7601770f921986985055a516bd1eef2127fbc72417c4328d9d' 
  AND token = 'CriURmX42WNDMvyKgqrF+iMw2Jhxc+kUdbzZVryQ/Wk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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