SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '503c8347aa5c4996ba7b9d202194bc42dcd2661092bd99d72912772f42166ddf' 
  AND token = 'Yp5+8WeGJ3D3Ic6nhMVKf9S/HWhiZm8ilDRfpCxjwFc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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