SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81f2c66d1ec669b45747552b0fbddab8063ba86d3b9b193fa0b0ece91e1b52d6' 
  AND token = 'dzITWGwCkkGU1rH62AQBYgqP+TwJH9f0zFIE5/1DulA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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