diff --git a/api/block_confirmation.go b/api/block_confirmation.go
index f96b523e..fc0ecdef 100644
--- a/api/block_confirmation.go
+++ b/api/block_confirmation.go
@@ -55,6 +55,9 @@ func (app *ApiServer) BlockConfirmation(c *fiber.Ctx) error {
 		return err
 	}
 
+	// Clients poll this until their block is indexed; a cached "not yet"
+	// keeps them waiting after it has been.
+	c.Set(fiber.HeaderCacheControl, "no-store")
 	return c.JSON(fiber.Map{
 		"data": res,
 	})
diff --git a/api/v1_unclaimed_id.go b/api/v1_unclaimed_id.go
index fe77126b..8ccb6408 100644
--- a/api/v1_unclaimed_id.go
+++ b/api/v1_unclaimed_id.go
@@ -34,6 +34,10 @@ func (app *ApiServer) v1UnclaimedId(c *fiber.Ctx, tableName, idField string, low
 	}
 
 	id, _ := trashid.EncodeHashId(freeId)
+	// Each response must be a fresh id: a cached one hands the same id to
+	// concurrent callers, and every write after the first that uses it is
+	// rejected as a duplicate.
+	c.Set(fiber.HeaderCacheControl, "no-store")
 	return c.JSON(fiber.Map{
 		"data": id,
 	})
diff --git a/api/v1_unclaimed_id_test.go b/api/v1_unclaimed_id_test.go
new file mode 100644
index 00000000..7e4d93df
--- /dev/null
+++ b/api/v1_unclaimed_id_test.go
@@ -0,0 +1,34 @@
+package api
+
+import (
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// An edge cache in front of these routes hands one response to every caller,
+// so each must tell caches not to store it.
+func TestUnclaimedIdAndBlockConfirmationAreNotCacheable(t *testing.T) {
+	app := emptyTestApp(t)
+
+	for _, path := range []string{
+		"/v1/users/unclaimed_id",
+		"/v1/tracks/unclaimed_id",
+		"/v1/playlists/unclaimed_id",
+		"/v1/playlists/unclaimed-id",
+		"/v1/comments/unclaimed_id",
+		"/v1/comments/unclaimed-id",
+		"/v1/events/unclaimed_id",
+		"/v1/events/unclaimed-id",
+		"/block_confirmation?blocknumber=1&blockhash=0xabc",
+		"/block-confirmation?blocknumber=1&blockhash=0xabc",
+	} {
+		t.Run(path, func(t *testing.T) {
+			res, err := app.Test(httptest.NewRequest("GET", path, nil), -1)
+			assert.NoError(t, err)
+			assert.Equal(t, 200, res.StatusCode)
+			assert.Equal(t, "no-store", res.Header.Get("Cache-Control"))
+		})
+	}
+}