SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '8c15369a1103749265f9dc111c0243d6db611573a43cccaabe4eedb2927032b2' 
  AND token = 'sMw0Y6pOa4r6Jcl+3YhDGmZN//akpTBtIiVXQapOY18=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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