diff --git a/.dockerignore b/.dockerignore
new file mode 100644
index 0000000..063d4cc
--- /dev/null
+++ b/.dockerignore
@@ -0,0 +1,28 @@
+# Docker does not read .gitignore, and a pattern here matches from the root of
+# the build context only: a pattern meant for every directory needs `**/`.
+
+.git
+
+# Local build and debug output: `make build`, `make run`, `make asupdate`, test
+# binaries, coverage profiles and source archives.
+/bin
+/log.txt
+/out
+/pkg/asinfo/asdata.json
+**/*.tar.zst
+**/*.test
+**/*.out
+**/*.tmp
+
+# Local databases and secrets. The image carries a source archive of the whole
+# build context, so these would otherwise ship inside it.
+**/*.db
+**/*.db-journal
+**/*.db-wal
+**/.env
+
+# A local Go workspace points at directories outside the build context.
+/go.work
+/go.work.sum
+
+**/.DS_Store
diff --git a/TODO.md b/TODO.md
index fbab888..03fd25f 100644
--- a/TODO.md
+++ b/TODO.md
@@ -24,12 +24,13 @@ https://git.eeqj.de/sneak/routewatch/pulls/6. After that, setting
 routewatch up under upaas on fsn1app1 and deploying it are his
 (https://git.eeqj.de/sneak/routewatch/issues/31), and so is the run under a
 real 5 GiB limit (https://git.eeqj.de/sneak/routewatch/issues/3).
-Nothing on the record orders
-https://git.eeqj.de/sneak/routewatch/issues/39 and
-https://git.eeqj.de/sneak/routewatch/issues/30.
+The other open issue is https://git.eeqj.de/sneak/routewatch/issues/30.
 
 # Completed Steps
 
+- 2026-09-29: `.dockerignore` keeps `.git`, local build output, local
+  databases and `.env` out of the Docker build context, and so out of the
+  source archive in the image (closes #39)
 - 2026-09-29: README first line names the MIT license and the author;
   the License section now says MIT and links `LICENSE`, and an Author
   section was added; this file brought up to date (closes #38)
@@ -102,4 +103,3 @@ https://git.eeqj.de/sneak/routewatch/issues/30.
 - `/api/v1/stats` answered HTTP 500 after 35 hours on the live feed, seen
   on `3898daa`, which predates the 2026-09-22 in-memory statistics
   (https://git.eeqj.de/sneak/routewatch/issues/30)
-- Add a `.dockerignore` (https://git.eeqj.de/sneak/routewatch/issues/39)