SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f284b840e3ee2e6227542eebf7dc7780b555c4f72d35d49322c1f10c77c3b327' 
  AND token = 'UdYcMQdATefDAAuYVf5EceCPoVX5aE33sVzGgXlXxDA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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