SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ddf5f3eb56431b359601912484134e2d1492abe320a4b632cc5aa921c644ba3a' 
  AND token = 'suwMoJrww8a7YuIYxS+YHLX2+7hEOe6HSkdbfTzGh1A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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