SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '53df968684595b7a05604c9a6560154cbbfc7dc4d2d5854e33a62c92df21aac4' 
  AND token = '4z+EG2lpaCyhE6kfOmH7znTaqKMFLaB53YU6NpXLgeY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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