SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd2fd3bafa435ffcecce152d26a529d4b25b7335fd9bf3d6d9a8074a764f2cb66' 
  AND token = 'r+JXnsUo7rYbGrYB3pWDwYWBUcDHeXvuH8MKwnciPmg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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