how to

[verbal axle]

Hi @delicate anvil. I'm kapa.ai, your friendly support bot. I will try to answer your question by searching through the knowledge base. :wave:

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To index users by their Convex-assigned ID, you generally do not need to create a custom index, because every Convex document already has a unique _id field, and you can always retrieve a user by their _id using db.get(id). However, if you want to create a custom index on a different id field (for example, if you have a custom string id), you can add an index like this:

users: defineTable({
  // ... your fields ...
  id: v.string(), // your custom id field
  // other fields...
}).index("byId", ["id"])

If you want to add an index on the built-in _id field, that's not necessary—Convex always allows efficient lookups by _id without a custom index.

If you are using the default users table from authTables, and you want to add a custom index, you can inline the table definition and add your index as shown above. For example, if you have a custom id field:

users: defineTable({
  id: v.string(),
  name: v.optional(v.string()),
  // ... other fields ...
}).index("byId", ["id"])

But for the built-in _id, just use db.get(id)—no index needed.

For reference, see the example of adding an index on a custom id field in the Lucia Auth Convex schema example:

users: defineTable({
  id: v.string(),
  email: v.string(),
}).index("byId", ["id"])

If you only need to look up users by their Convex _id, you do not need to add any index at all—just use db.get(id) as provided by Convex out of the box.

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