SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '1b3ababdafe95034d7b42c6da5b5691e79f61e049632cc0cd8b5839b9d256993' 
  AND token = 'YgJ/WWVDl7AleRH/5pUCvOCf2a1FFGtFwNbwtxDzTI8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

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