diff --git a/tests/test_tle_store.py b/tests/test_tle_store.py
index f56a9ad..77cc68f 100644
--- a/tests/test_tle_store.py
+++ b/tests/test_tle_store.py
@@ -1,5 +1,7 @@
 """Tests for the unified TLE store."""
 
+from pathlib import Path
+
 import pytest
 
 from utils import tle_store
@@ -46,3 +48,45 @@ class TestTLEStore:
         tle_store.update({"TEST-SAT": SAMPLE})
         tle_store._reset_for_tests()
         assert tle_store.get_tle("TEST-SAT") == SAMPLE
+
+    def test_update_before_first_read_keeps_seed(self):
+        """An update() on a fresh DB must not prevent the static seed."""
+        tle_store.update({"TEST-SAT": SAMPLE})
+        tles = tle_store.all_tles()
+        assert "TEST-SAT" in tles
+        assert "ISS" in tles  # static seed still present
+
+    def test_update_waits_for_concurrent_writer(self):
+        """A short-lived writer in another connection must not make update() raise."""
+        import sqlite3
+        import threading
+
+        tle_store.all_tles()  # ensure DB exists
+        blocker = sqlite3.connect(str(tle_store._DB_PATH), check_same_thread=False)
+        blocker.execute("BEGIN IMMEDIATE")
+
+        def release_soon():
+            import time
+
+            time.sleep(0.2)
+            blocker.commit()
+            blocker.close()
+
+        t = threading.Thread(target=release_soon)
+        t.start()
+        tle_store.update({"TEST-SAT": SAMPLE})  # must block briefly, not raise
+        t.join()
+        assert tle_store.get_tle("TEST-SAT") == SAMPLE
+
+
+def test_default_db_path_points_at_instance_dir():
+    """The unpatched module constant must resolve to <repo>/instance/tle.db."""
+    import importlib
+
+    spec = importlib.util.find_spec("utils.tle_store")
+    module_file = Path(spec.origin)
+    expected = module_file.parent.parent / "instance" / "tle.db"
+    # Read the constant from a fresh module instance, not the patched one
+    fresh = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(fresh)
+    assert expected == fresh._DB_PATH
diff --git a/utils/tle_store.py b/utils/tle_store.py
index 7bd99dc..ee20edd 100644
--- a/utils/tle_store.py
+++ b/utils/tle_store.py
@@ -24,8 +24,9 @@ _cache: dict[str, tuple[str, str, str]] | None = None
 
 def _connect() -> sqlite3.Connection:
     _DB_PATH.parent.mkdir(parents=True, exist_ok=True)
-    conn = sqlite3.connect(str(_DB_PATH), check_same_thread=False)
+    conn = sqlite3.connect(str(_DB_PATH), check_same_thread=False, timeout=5)
     conn.execute("PRAGMA journal_mode = WAL")
+    conn.execute("PRAGMA busy_timeout = 5000")
     conn.execute(
         """
         CREATE TABLE IF NOT EXISTS tle_entries (
@@ -37,6 +38,7 @@ def _connect() -> sqlite3.Connection:
         )
         """
     )
+    _seed_if_empty(conn)
     return conn
 
 
@@ -64,8 +66,10 @@ def _load() -> dict[str, tuple[str, str, str]]:
             if _cache is None:
                 conn = _connect()
                 try:
-                    _seed_if_empty(conn)
                     rows = conn.execute("SELECT key, name, line1, line2 FROM tle_entries").fetchall()
+                    # Single-statement assignment of the fully built dict —
+                    # the DCL pattern is only safe because readers never see
+                    # a partially populated cache
                     _cache = {key: (name, l1, l2) for key, name, l1, l2 in rows}
                 finally:
                     conn.close()