SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '79a21ed851129a56f4f48a15f1eda8c1b46eceb7daafcecc06132b4f1ce72d65' 
  AND token = 'S/8uTFwVcBKldvKw2nZLCGKMXHzEmkDQm6ngTmRzjuE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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