SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'bf7661adb69b71f5a54f46ce39f3bdd84af48b00cb649bb98da2689d3db3b29c' 
  AND token = 'UeW2QVPo/q48VmWeyWL6eIl8MqBxbNtj3cH98a+v2Ks=' 
  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"
    }
  }
}