Signal Forge ADR-010: gRPC server-streaming via AsAsyncEnumerable (not ToListAsync)

Status: Accepted

Decision: GetOrdersByProject streams rows directly from the PostgreSQL cursor using AsAsyncEnumerable(), writing each row to the gRPC stream as it is fetched.

Code pattern:

await foreach (var order in _db.Orders
    .Where(o => o.ProjectId == request.ProjectId)
    .OrderByDescending(o => o.CreatedAt)
    .AsAsyncEnumerable()
    .WithCancellation(context.CancellationToken))
{
    await responseStream.WriteAsync(MapToResponse(order), context.CancellationToken);
}

Rationale:

ToListAsync() loads all matching rows into a List<Order> in application memory before streaming begins. For large result sets this causes OOM.
AsAsyncEnumerable() uses the database cursor: one row is fetched, sent over gRPC, then the next is fetched. Memory usage is O(1) regardless of result set size.
CancellationToken is threaded through so the DB query is cancelled if the gRPC client disconnects.

Alternative considered: ToListAsync() — rejected due to unbounded memory growth.