Object keeps getting overwritten

I feel like i'm missing something fundamental here. when I add a new entry into object b it resets to an empty object upon a subsequent request. Can anyone help?

  addNewTicket: ticketsDomainProcedure
    .input(
      z.object({
        id: z.string(),
        title: z.string(),
        description: z.string(),
        type: z.string(),
        status: z.string(),
      })
    )
    .mutation(async (req) => {
      const b = {};

      console.log('original', b);

      const tenantId = '908e2d94-aef7-4ba6-a1a3-2ccec65a1d97';

      const updatedState = {
        ...b,
        [req.input.id]: {
          id: req.input.id,
          tenantId: tenantId,
          title: req.input.title,
          description: req.input.description,
          type: req.input.type,
          status: req.input.status,
        },
      };

      console.log('NEW STATE', updatedState);

      return updatedState;
    }),
});

tRPC procedures re-run on every request, so every time a request comes in, it creates a new object b.
To preserve state you'll have to declare the object outside of the trpc routers/procedures, or better yet, use some sort of database

thank you!