SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c15f778684ed4a098e273f397713663bfeff84485e6937769ec40a7e41644aab' 
  AND token = 'CbdyxmGHQqIFMeGIwRUt3CWEyIE7VlEJsK+cRSCoOpM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}