From 55db013dfbb4864420816e53c3bd52039a893ba0 Mon Sep 17 00:00:00 2001
From: "Timothy J. Aveni" <tja@berkeley.edu>
Date: Tue, 30 Jun 2026 07:18:55 -0700
Subject: [PATCH] Increase AMI builder capacity

---
 main.tf      | 16 +++++++++++-----
 variables.tf | 28 ++++++++++++++++++++++++++--
 2 files changed, 37 insertions(+), 7 deletions(-)

diff --git a/main.tf b/main.tf
index 9a305fa..ec695bf 100644
--- a/main.tf
+++ b/main.tf
@@ -46,10 +46,11 @@ locals {
     ? "nixos/*-${var.system}"
     : var.base_nixos_ami_name_pattern
   )
-  base_nixos_ami_id = var.base_nixos_ami_id == null ? data.aws_ami.nixos[0].id : var.base_nixos_ami_id
-  resource_name     = "${var.name}-builder-${local.aws_architecture}-${substr(var.input_hash, 0, 12)}"
-  nix_device_id     = replace(aws_ebs_volume.nix.id, "-", "")
-  nix_device        = "/dev/disk/by-id/nvme-Amazon_Elastic_Block_Store_${local.nix_device_id}"
+  builder_instance_type = var.builder_instance_type == null ? (var.system == "aarch64-linux" ? "c7g.2xlarge" : "c7i.2xlarge") : var.builder_instance_type
+  base_nixos_ami_id     = var.base_nixos_ami_id == null ? data.aws_ami.nixos[0].id : var.base_nixos_ami_id
+  resource_name         = "${var.name}-builder-${local.aws_architecture}-${substr(var.input_hash, 0, 12)}"
+  nix_device_id         = replace(aws_ebs_volume.nix.id, "-", "")
+  nix_device            = "/dev/disk/by-id/nvme-Amazon_Elastic_Block_Store_${local.nix_device_id}"
   tags = {
     Name          = local.resource_name
     Project       = var.name
@@ -114,6 +115,8 @@ resource "aws_ebs_volume" "nix" {
   availability_zone = data.aws_subnet.selected.availability_zone
   size              = var.nix_volume_size_gb
   type              = "gp3"
+  iops              = var.nix_volume_iops
+  throughput        = var.nix_volume_throughput
 
   tags = merge(local.tags, {
     Name = "${local.resource_name}-nix"
@@ -122,11 +125,12 @@ resource "aws_ebs_volume" "nix" {
 
 resource "aws_instance" "builder" {
   ami                         = local.base_nixos_ami_id
-  instance_type               = var.builder_instance_type
+  instance_type               = local.builder_instance_type
   subnet_id                   = local.subnet_id
   vpc_security_group_ids      = [aws_security_group.builder.id]
   iam_instance_profile        = aws_iam_instance_profile.builder.name
   associate_public_ip_address = true
+  ebs_optimized               = true
   key_name                    = var.ssh_public_key == null ? null : aws_key_pair.admin[0].key_name
   user_data_replace_on_change = true
 
@@ -143,6 +147,8 @@ resource "aws_instance" "builder" {
   root_block_device {
     volume_size = var.root_volume_size_gb
     volume_type = "gp3"
+    iops        = var.root_volume_iops
+    throughput  = var.root_volume_throughput
   }
 
   tags = local.tags
diff --git a/variables.tf b/variables.tf
index 36cfae8..b45fddb 100644
--- a/variables.tf
+++ b/variables.tf
@@ -38,8 +38,8 @@ variable "flake_lock_rev" {
 
 variable "builder_instance_type" {
   type        = string
-  default     = "t4g.large"
-  description = "Temporary EC2 instance type used to build and seed the AMI."
+  default     = null
+  description = "Temporary EC2 instance type used to build and seed the AMI. Defaults to c7g.2xlarge for aarch64-linux and c7i.2xlarge for x86_64-linux."
 }
 
 variable "vpc_id" {
@@ -78,12 +78,36 @@ variable "root_volume_size_gb" {
   description = "Temporary builder root EBS volume size. This becomes the final AMI root snapshot size."
 }
 
+variable "root_volume_iops" {
+  type        = number
+  default     = 6000
+  description = "Temporary builder root gp3 IOPS. This affects builder speed only; snapshots do not preserve provisioned IOPS."
+}
+
+variable "root_volume_throughput" {
+  type        = number
+  default     = 250
+  description = "Temporary builder root gp3 throughput in MiB/s. This affects builder speed only; snapshots do not preserve provisioned throughput."
+}
+
 variable "nix_volume_size_gb" {
   type        = number
   default     = 50
   description = "Temporary /nix EBS volume size. This becomes the final AMI /nix snapshot size."
 }
 
+variable "nix_volume_iops" {
+  type        = number
+  default     = 12000
+  description = "Temporary /nix gp3 IOPS used while building and seeding the AMI."
+}
+
+variable "nix_volume_throughput" {
+  type        = number
+  default     = 500
+  description = "Temporary /nix gp3 throughput in MiB/s used while building and seeding the AMI."
+}
+
 variable "nix_pool" {
   type        = string
   default     = "nixos-zfs-nix"