diff --git a/.github/workflows/rebuild-hmpxv1-big.yaml b/.github/workflows/rebuild-hmpxv1-big.yaml
index 6ac2831c..c5420b67 100644
--- a/.github/workflows/rebuild-hmpxv1-big.yaml
+++ b/.github/workflows/rebuild-hmpxv1-big.yaml
@@ -50,12 +50,16 @@ jobs:
         SLACK_CHANNELS: ${{ inputs.trial_name && vars.TEST_SLACK_CHANNEL || vars.SLACK_CHANNELS }}
         BUILD_DIR: phylogenetic
         BUILD_NAME: hmpxv1_big
+      # Aiming to use c7a.8xlarge instances since previous runs with c7a.4xlarge
+      # failed with OOM error. Note c7a.8xlarge is the largest instance allowed
+      # for the default nextstrain-job-queue. If this needs more memory,
+      # consider adding a separate job queue for larger instances.
       run: |
         nextstrain build \
           --detach \
           --no-download \
-          --cpus 16 \
-          --memory 28GiB \
+          --cpus 32 \
+          --memory 60GiB \
           --env GITHUB_RUN_ID \
           --env SLACK_TOKEN \
           --env SLACK_CHANNELS \
diff --git a/.github/workflows/rebuild-hmpxv1.yaml b/.github/workflows/rebuild-hmpxv1.yaml
index 97a993ec..01265586 100644
--- a/.github/workflows/rebuild-hmpxv1.yaml
+++ b/.github/workflows/rebuild-hmpxv1.yaml
@@ -50,12 +50,14 @@ jobs:
         SLACK_CHANNELS: ${{ inputs.trial_name && vars.TEST_SLACK_CHANNEL || vars.SLACK_CHANNELS }}
         BUILD_DIR: phylogenetic
         BUILD_NAME: hmpxv1
+      # Aiming for c7a.xlarge instances since previous run with c7a.large failed
+      # with OOM error.
       run: |
         nextstrain build \
           --detach \
           --no-download \
-          --cpus 2 \
-          --memory 4GiB \
+          --cpus 4 \
+          --memory 7GiB \
           --env GITHUB_RUN_ID \
           --env SLACK_TOKEN \
           --env SLACK_CHANNELS \
diff --git a/.github/workflows/rebuild-mpxv.yaml b/.github/workflows/rebuild-mpxv.yaml
index 382fdef1..d170baa6 100644
--- a/.github/workflows/rebuild-mpxv.yaml
+++ b/.github/workflows/rebuild-mpxv.yaml
@@ -50,12 +50,14 @@ jobs:
         SLACK_CHANNELS: ${{ inputs.trial_name && vars.TEST_SLACK_CHANNEL || vars.SLACK_CHANNELS }}
         BUILD_DIR: phylogenetic
         BUILD_NAME: mpxv
+      # Aiming for c7a.2xlarge instances since previous run with c7a.xlarge
+      # failed with OOM error.
       run: |
         nextstrain build \
           --detach \
           --no-download \
-          --cpus 2 \
-          --memory 4GiB \
+          --cpus 8 \
+          --memory 14GiB \
           --env GITHUB_RUN_ID \
           --env SLACK_TOKEN \
           --env SLACK_CHANNELS \