+ query BlogIndex($topic: String) {
- query BlogIndex {
    allMdx(
+     filter: { frontmatter: { isArchive: { nin: true } }, topics: { in: [$topic] } } 
-      filter: { frontmatter: { isArchive: { nin: true } } }
      sort: { fields: frontmatter___date, order: DESC }
    ) {
      nodes {
        id
        slug
        frontmatter {
          title
          date(formatString: "MMMM DD, YYYY")
          topics
        }
      }
    }
  }