SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = 'b8649428eaa146a504ff16b580dd7ff09646ab5689d47ab41773f84a59b7bd95' 
  AND token = 'a+H2nzCdttUxc8exkb0bDTu77quisMwg58e9Z2o2yIU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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