SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3e6debfaebe618d9cf82fa91bf62bc03a36f4e535f194a708272e4e1fd351988' 
  AND token = 'bPmvNnouo8pvFPiMHRTshRFwZosYkbgv2IG1XdRXw34=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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