SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b9d2f879fc748fd2f2ec64ea884ea5c2fc65b74d79bc01bf41507d58a49549b5' 
  AND token = '4yxx/3NDnVkT5nZoUrQlYlmOJ3JjjVRQYcKHgd08LWU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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