SOLVED - You can only do updates via a PK, you can’t do them with a GSIPK so I had to swap them 🎉 . Thanks to Garret for that. I’m doing something goofy with a DynamoDB request. Or I set up a SKI incorrectly (seems unlikely) I recently added a GSI to my table

customersTable.addGlobalIndexes({
      gsi1pk: {
        partitionKey: "gsi1pk",
        type: sst.TableFieldType.STRING,
      },
    });

I can see it in my Indexes so that appears to have worked. When I add params to put like so…

const params = {
      TableName: process.env.TABLE_NAME,
      Item: {
        pk: `SHOP#${shop}PHONE#${phoneNumber}`,
        sk: `SID#${messageSid}`,
        gsi1pk: `SID#${messageSid}`,
        messageStatus,
      },
    };

    await dynamoDb.put(params);

the item is inserted in the table and I can see it 🎉 However, when I try to update that value

const values = {
    TableName: process.env.TABLE_NAME,
    Key: {
      gsi1pk: `SID#${messageSid}`,
      sk: `SID#${messageSid}`,
    },
    UpdateExpression: "SET messageStatus = :messageStatus",
    ExpressionAttributeValues: {
      ":messageStatus": smsStatus,
    },
  };

  await dynamoDb.update(values);

It’s not obvious to me what’s wrong.

You cant update an item by a secondary index only query.

I don’t think I understand that sentence

You can only update an item by the primary key. GSI's are only allowed to be queried

oh really. So, I should swap the PK and GSI