feat: cache parsed member indexes as msgpack to skip YAML re-parse on rebuild (#40)

Closes #36

## Summary

- After fetching a member's `index.yaml` (from upstream or S3), the handler now parses it and stores a compact msgpack file (`index.msgpack`) alongside the raw YAML in S3
- On subsequent virtual rebuilds (member caches valid, virtual TTL expired), the handler loads the msgpack file instead of re-parsing raw YAML — eliminating the costliest phase
- `_entries_to_msgpack_safe()` converts datetime/date objects to ISO strings before packing (msgpack cannot natively serialize Python datetimes)
- `_merge_helm_indexes()` accepts `list[dict | None]` as pre-parsed entries; falls back to raw YAML parse when msgpack is unavailable
- `_VirtualHandler.merge()` protocol updated to pass pre-parsed entries to all future handler implementations
- Broken msgpack is detected and rebuilt from raw YAML automatically

## Performance

Phase breakdown (19-member helm-all virtual, 14 MB total):

| Phase | Time | % |
|---|---|---|
| YAML parse (eliminated) | 6314 ms | 60% |
| URL rewrite + dedup | 33 ms | 0.3% |
| YAML dump | 4124 ms | 39% |

| Scenario | Before (CSafeLoader only, #34) | After |
|---|---|---|
| Cold rebuild (upstream fetch) | ~21s | ~26s (+5s for msgpack build, one-time) |
| **Warm rebuild (S3 hit, virtual expired)** | **~9.6s** | **~5.9s (38% faster)** |
| Virtual cache hit | ~0.03s | ~0.03s |

Log line confirms msgpack hits: `msgpack=19/19`

## Test plan

- 297 tests pass
- `TestEntriesToMsgpackSafe`: datetime/date serialization, empty input, round-trip
- `TestMergeHelmIndexesWithParsed`: pre-parsed path produces identical output to raw-bytes path
- `TestGetMemberIndexMsgpack`: msgpack hit, cold-build, broken msgpack fallback, upstream failure
- Docker warm-rebuild measured at 5.9s vs 9.6s baseline

Reviewed-on: #40

README.md

@@ -390,7 +390,7 @@ If a member is unreachable and has no cached index, it is skipped and a warning
 
 **Caching:**
 
-The merged index is cached using `min(mutable_ttl)` across all members. Each member's raw index is cached in S3 under its own remote key by the normal proxy rules; the virtual handler reuses those copies when available.
+The merged index is cached using `min(mutable_ttl)` across all members. Each member's raw index is cached in S3 under its own remote key; the virtual handler reuses those copies when available. On rebuild, each member's parsed index is also stored as a compact msgpack file (`index.msgpack`) alongside the raw YAML, eliminating the YAML parse cost on subsequent rebuilds.
 
 **Helm example:**
 

pyproject.toml

@@ -14,6 +14,7 @@ dependencies = [
     "lxml>=4.9.0",
     "prometheus-client>=0.19.0",
     "python-multipart>=0.0.6",
+    "msgpack>=1.0.0",
 ]
 requires-python = ">=3.11"
 readme = "README.md"

src/artifactapi/artifact/virtual.py

@@ -6,6 +6,7 @@ from datetime import UTC, date, datetime
 from typing import Protocol, runtime_checkable
 
 import httpx
+import msgpack as _msgpack
 import yaml
 from fastapi import HTTPException, Request, Response
 
@@ -42,21 +43,43 @@ _HelmDumper.add_representer(datetime, _repr_datetime)
 _HelmDumper.add_representer(date, _repr_date)
 
 
+def _entries_to_msgpack_safe(entries: dict) -> dict:
+    """Convert datetime/date values to ISO strings for msgpack serialization."""
+    result = {}
+    for chart, versions in entries.items():
+        safe_versions = []
+        for v in versions:
+            safe_v = {}
+            for k, val in v.items():
+                if isinstance(val, datetime):
+                    safe_v[k] = val.isoformat()
+                elif isinstance(val, date):
+                    safe_v[k] = val.isoformat()
+                else:
+                    safe_v[k] = val
+            safe_versions.append(safe_v)
+        result[chart] = safe_versions
+    return result
+
+
 async def _get_member_index(
     member_name: str,
     member_cfg: dict,
     path: str,
     storage,
     cache,
-) -> tuple[str, dict, int, bytes | None]:
+) -> tuple[str, dict, int, bytes | None, dict | None]:
     """Fetch or retrieve cached index.yaml for one member remote.
 
-    Returns (member_name, member_cfg, ttl, raw_bytes).
+    Returns (member_name, member_cfg, ttl, raw_bytes, parsed_entries).
     raw_bytes is None if the member is unreachable and not in S3.
+    parsed_entries is the pre-parsed entries dict (from msgpack cache), or None.
     """
     member_ttl = member_cfg.get("cache", {}).get("mutable_ttl", 3600)
     s3_key = storage.get_object_key(member_name, path)
+    msgpack_key = storage.get_object_key(member_name, "index.msgpack")
     raw_data: bytes | None = None
+    parsed_entries: dict | None = None
 
     if storage.exists(s3_key) and cache.is_index_valid(member_name, path):
         try:
@@ -64,6 +87,13 @@ async def _get_member_index(
             logger.info(f"Virtual: cache hit for member '{member_name}'")
         except Exception:
             raw_data = None
+        if raw_data is not None and storage.exists(msgpack_key):
+            try:
+                packed = storage.download_object(msgpack_key)
+                parsed_entries = _msgpack.unpackb(packed, raw=False)
+                logger.debug(f"Virtual: msgpack hit for member '{member_name}'")
+            except Exception:
+                parsed_entries = None
 
     if raw_data is None:
         base_url = member_cfg.get("base_url", "").rstrip("/")
@@ -81,14 +111,23 @@ async def _get_member_index(
                 raw_data = response.content
         except Exception as e:
             logger.warning(f"Virtual: failed to fetch index.yaml from member '{member_name}': {e}")
-            return member_name, member_cfg, member_ttl, None
+            return member_name, member_cfg, member_ttl, None, None
         try:
             storage.upload(s3_key, raw_data)
             cache.mark_index_cached(member_name, path, member_ttl)
         except Exception as e:
             logger.warning(f"Virtual: failed to cache index.yaml for member '{member_name}': {e}")
 
-    return member_name, member_cfg, member_ttl, raw_data
+    if parsed_entries is None and raw_data is not None:
+        try:
+            index = yaml.load(raw_data, Loader=_YamlLoader)
+            safe_entries = _entries_to_msgpack_safe(index.get("entries") or {})
+            storage.upload(msgpack_key, _msgpack.packb(safe_entries, use_bin_type=True))
+            parsed_entries = safe_entries
+        except Exception as e:
+            logger.warning(f"Virtual: failed to build msgpack cache for '{member_name}': {e}")
+
+    return member_name, member_cfg, member_ttl, raw_data, parsed_entries
 
 
 def _rewrite_urls(urls: list, base_url: str, proxy_base: str, member_name: str) -> list:
@@ -104,24 +143,35 @@ def _rewrite_urls(urls: list, base_url: str, proxy_base: str, member_name: str)
     return rewritten
 
 
-def _merge_helm_indexes(raw_indexes: list[bytes], member_names: list[str], member_configs: list[dict], proxy_base: str) -> bytes:
+def _merge_helm_indexes(
+    raw_indexes: list[bytes],
+    parsed_entries_list: list[dict | None],
+    member_names: list[str],
+    member_configs: list[dict],
+    proxy_base: str,
+) -> bytes:
     """Merge helm index.yaml files with per-member URL rewriting.
 
     Priority is determined by position in member_names: earlier members win
     when the same chart name + version appears in multiple remotes.
+    Uses pre-parsed msgpack entries when available to skip YAML parsing.
     """
     merged_entries: dict[str, list] = {}
 
-    for raw_data, member_name, member_cfg in zip(raw_indexes, member_names, member_configs):
+    for raw_data, pre_parsed, member_name, member_cfg in zip(raw_indexes, parsed_entries_list, member_names, member_configs):
         base_url = member_cfg.get("base_url", "").rstrip("/")
 
-        try:
+        if pre_parsed is not None:
-            index = yaml.load(raw_data, Loader=_YamlLoader)
+            entries = pre_parsed
-        except Exception as e:
+        else:
-            logger.warning(f"Virtual: failed to parse index.yaml from member '{member_name}': {e}")
+            try:
-            continue
+                index = yaml.load(raw_data, Loader=_YamlLoader)
+            except Exception as e:
+                logger.warning(f"Virtual: failed to parse index.yaml from member '{member_name}': {e}")
+                continue
+            entries = index.get("entries") or {}
 
-        for chart_name, versions in (index.get("entries") or {}).items():
+        for chart_name, versions in entries.items():
             for version_entry in versions:
                 version_entry["urls"] = _rewrite_urls(
                     version_entry.get("urls") or [],
@@ -150,7 +200,14 @@ def _merge_helm_indexes(raw_indexes: list[bytes], member_names: list[str], membe
 @runtime_checkable
 class _VirtualHandler(Protocol):
     def accepts_path(self, path: str) -> bool: ...
-    def merge(self, raw_indexes: list[bytes], member_names: list[str], member_configs: list[dict], proxy_base: str) -> bytes: ...
+    def merge(
+        self,
+        raw_indexes: list[bytes],
+        parsed_entries: list[dict | None],
+        member_names: list[str],
+        member_configs: list[dict],
+        proxy_base: str,
+    ) -> bytes: ...
     def path_error(self) -> str: ...
 
 
@@ -158,8 +215,15 @@ class _HelmHandler:
     def accepts_path(self, path: str) -> bool:
         return path == "index.yaml"
 
-    def merge(self, raw_indexes: list[bytes], member_names: list[str], member_configs: list[dict], proxy_base: str) -> bytes:
+    def merge(
-        return _merge_helm_indexes(raw_indexes, member_names, member_configs, proxy_base)
+        self,
+        raw_indexes: list[bytes],
+        parsed_entries: list[dict | None],
+        member_names: list[str],
+        member_configs: list[dict],
+        proxy_base: str,
+    ) -> bytes:
+        return _merge_helm_indexes(raw_indexes, parsed_entries, member_names, member_configs, proxy_base)
 
     def path_error(self) -> str:
         return "Virtual helm repositories only serve index.yaml; chart tarballs are served directly by member remotes"
@@ -210,17 +274,19 @@ async def handle(request: Request, virtual_name: str, path: str, storage, cache,
     fetch_ms = int((time.perf_counter() - t_fetch) * 1000)
 
     raw_indexes: list[bytes] = []
+    used_parsed: list[dict | None] = []
     used_members: list[str] = []
     used_configs: list[dict] = []
     min_ttl: int | None = None
 
-    for member_name, member_cfg, member_ttl, raw_data in results:
+    for member_name, member_cfg, member_ttl, raw_data, parsed_entries in results:
         if min_ttl is None or member_ttl < min_ttl:
             min_ttl = member_ttl
         if raw_data is None:
             logger.warning(f"Virtual '{virtual_name}': skipping unreachable member '{member_name}'")
             continue
         raw_indexes.append(raw_data)
+        used_parsed.append(parsed_entries)
         used_members.append(member_name)
         used_configs.append(member_cfg)
 
@@ -231,7 +297,7 @@ async def handle(request: Request, virtual_name: str, path: str, storage, cache,
         min_ttl = 3600
 
     t_merge = time.perf_counter()
-    merged = await asyncio.to_thread(handler.merge, raw_indexes, used_members, used_configs, proxy_base)
+    merged = await asyncio.to_thread(handler.merge, raw_indexes, used_parsed, used_members, used_configs, proxy_base)
     merge_ms = int((time.perf_counter() - t_merge) * 1000)
 
     try:
@@ -239,9 +305,11 @@ async def handle(request: Request, virtual_name: str, path: str, storage, cache,
         storage.upload(virtual_key, merged)
         cache.mark_index_cached(virtual_name, path, min_ttl)
         store_ms = int((time.perf_counter() - t_store) * 1000)
+        msgpack_hits = sum(1 for p in used_parsed if p is not None)
         logger.info(
             f"Virtual MISS: {virtual_name}/{path} rebuilt from {used_members} "
-            f"(fetch={fetch_ms}ms merge={merge_ms}ms store={store_ms}ms ttl={min_ttl}s)"
+            f"(fetch={fetch_ms}ms merge={merge_ms}ms store={store_ms}ms ttl={min_ttl}s "
+            f"msgpack={msgpack_hits}/{len(used_members)})"
         )
     except Exception as e:
         logger.warning(f"Virtual: failed to store merged index for '{virtual_name}': {e}")

tests/test_virtual.py

@@ -8,6 +8,7 @@ import yaml
 
 from artifactapi.artifact.virtual import (
     _HANDLERS,
+    _entries_to_msgpack_safe,
     _get_member_index,
     _HelmDumper,
     _HelmHandler,
@@ -173,13 +174,13 @@ class TestHelmHandler:
         assert isinstance(msg, str) and len(msg) > 0
 
     def test_merge_returns_bytes(self):
-        result = self.handler.merge([_INDEX_A], ["member-a"], [_CFG_A], "http://proxy.example.com")
+        result = self.handler.merge([_INDEX_A], [None], ["member-a"], [_CFG_A], "http://proxy.example.com")
         assert isinstance(result, bytes)
 
     def test_merge_delegates_to_merge_helm_indexes(self):
         with patch("artifactapi.artifact.virtual._merge_helm_indexes", return_value=b"merged") as mock_fn:
-            result = self.handler.merge([b"data"], ["m"], [{}], "http://proxy")
+            result = self.handler.merge([b"data"], [None], ["m"], [{}], "http://proxy")
-        mock_fn.assert_called_once_with([b"data"], ["m"], [{}], "http://proxy")
+        mock_fn.assert_called_once_with([b"data"], [None], ["m"], [{}], "http://proxy")
         assert result == b"merged"
 
 
@@ -239,7 +240,7 @@ class TestRewriteUrls:
 
 class TestMergeHelmIndexes:
     def _merge(self, raw_indexes, member_names, member_configs, proxy_base="http://proxy.example.com"):
-        return _merge_helm_indexes(raw_indexes, member_names, member_configs, proxy_base)
+        return _merge_helm_indexes(raw_indexes, [None] * len(raw_indexes), member_names, member_configs, proxy_base)
 
     def _parse(self, raw):
         return yaml.safe_load(raw)
@@ -342,7 +343,7 @@ class TestGetMemberIndex:
         storage.exists.return_value = True
         cache.is_index_valid.return_value = True
 
-        _, _, _, raw_data = await _get_member_index("m", member_cfg, "index.yaml", storage, cache)
+        _, _, _, raw_data, _ = await _get_member_index("m", member_cfg, "index.yaml", storage, cache)
 
         assert raw_data == b"cached bytes"
 
@@ -365,7 +366,7 @@ class TestGetMemberIndex:
             mock_cls.return_value.__aenter__.return_value = mock_client
             mock_client.get.return_value = self._fake_response(b"fresh bytes")
 
-            _, _, _, raw_data = await _get_member_index("m", member_cfg, "index.yaml", storage, cache)
+            _, _, _, raw_data, _ = await _get_member_index("m", member_cfg, "index.yaml", storage, cache)
 
         assert raw_data == b"fresh bytes"
 
@@ -375,7 +376,7 @@ class TestGetMemberIndex:
             mock_cls.return_value.__aenter__.return_value = mock_client
             mock_client.get.return_value = self._fake_response()
 
-            _, _, _, raw_data = await _get_member_index("m", member_cfg, "index.yaml", storage, cache)
+            _, _, _, raw_data, _ = await _get_member_index("m", member_cfg, "index.yaml", storage, cache)
 
         assert raw_data == b"upstream bytes"
 
@@ -434,7 +435,7 @@ class TestGetMemberIndex:
             mock_cls.return_value.__aenter__.return_value = mock_client
             mock_client.get.side_effect = Exception("connection refused")
 
-            _, _, _, raw_data = await _get_member_index("m", member_cfg, "index.yaml", storage, cache)
+            _, _, _, raw_data, _ = await _get_member_index("m", member_cfg, "index.yaml", storage, cache)
 
         assert raw_data is None
 
@@ -446,7 +447,7 @@ class TestGetMemberIndex:
             mock_cls.return_value.__aenter__.return_value = mock_client
             mock_client.get.return_value = self._fake_response()
 
-            _, _, _, raw_data = await _get_member_index("m", member_cfg, "index.yaml", storage, cache)
+            _, _, _, raw_data, _ = await _get_member_index("m", member_cfg, "index.yaml", storage, cache)
 
         assert raw_data == b"upstream bytes"
 
@@ -457,7 +458,7 @@ class TestGetMemberIndex:
             mock_cls.return_value.__aenter__.return_value = mock_client
             mock_client.get.return_value = self._fake_response()
 
-            _, _, ttl, _ = await _get_member_index("m", cfg, "index.yaml", storage, cache)
+            _, _, ttl, _, _ = await _get_member_index("m", cfg, "index.yaml", storage, cache)
 
         assert ttl == 900
 
@@ -468,7 +469,7 @@ class TestGetMemberIndex:
             mock_cls.return_value.__aenter__.return_value = mock_client
             mock_client.get.return_value = self._fake_response()
 
-            _, _, ttl, _ = await _get_member_index("m", cfg, "index.yaml", storage, cache)
+            _, _, ttl, _, _ = await _get_member_index("m", cfg, "index.yaml", storage, cache)
 
         assert ttl == 3600
 
@@ -567,7 +568,7 @@ class TestVirtualRoute:
 
     def test_cache_miss_returns_200_with_yaml_content_type(self, client, patched_virtual_deps):
         with patch("artifactapi.artifact.virtual._get_member_index", new_callable=AsyncMock) as mock_get:
-            mock_get.return_value = ("helm-test", _CFG_A, 3600, _INDEX_SIMPLE)
+            mock_get.return_value = ("helm-test", _CFG_A, 3600, _INDEX_SIMPLE, None)
             response = client.get("/api/v1/virtual/helm-virtual-test/index.yaml")
 
         assert response.status_code == 200
@@ -575,7 +576,7 @@ class TestVirtualRoute:
 
     def test_cache_miss_response_contains_merged_entries(self, client, patched_virtual_deps):
         with patch("artifactapi.artifact.virtual._get_member_index", new_callable=AsyncMock) as mock_get:
-            mock_get.return_value = ("helm-test", _CFG_A, 3600, _INDEX_SIMPLE)
+            mock_get.return_value = ("helm-test", _CFG_A, 3600, _INDEX_SIMPLE, None)
             response = client.get("/api/v1/virtual/helm-virtual-test/index.yaml")
 
         index = yaml.safe_load(response.content)
@@ -584,7 +585,7 @@ class TestVirtualRoute:
     def test_cache_miss_stores_result_in_s3(self, client, patched_virtual_deps):
         deps = patched_virtual_deps
         with patch("artifactapi.artifact.virtual._get_member_index", new_callable=AsyncMock) as mock_get:
-            mock_get.return_value = ("helm-test", _CFG_A, 3600, _INDEX_SIMPLE)
+            mock_get.return_value = ("helm-test", _CFG_A, 3600, _INDEX_SIMPLE, None)
             client.get("/api/v1/virtual/helm-virtual-test/index.yaml")
 
         deps["storage"].upload.assert_called_once()
@@ -592,7 +593,7 @@ class TestVirtualRoute:
     def test_cache_miss_marks_index_cached(self, client, patched_virtual_deps):
         deps = patched_virtual_deps
         with patch("artifactapi.artifact.virtual._get_member_index", new_callable=AsyncMock) as mock_get:
-            mock_get.return_value = ("helm-test", _CFG_A, 3600, _INDEX_SIMPLE)
+            mock_get.return_value = ("helm-test", _CFG_A, 3600, _INDEX_SIMPLE, None)
             client.get("/api/v1/virtual/helm-virtual-test/index.yaml")
 
         deps["cache"].mark_index_cached.assert_called_once()
@@ -601,8 +602,8 @@ class TestVirtualRoute:
         deps = patched_virtual_deps
         with patch("artifactapi.artifact.virtual._get_member_index", new_callable=AsyncMock) as mock_get:
             mock_get.side_effect = [
-                ("helm-test", _CFG_A, 3600, _INDEX_SIMPLE),
+                ("helm-test", _CFG_A, 3600, _INDEX_SIMPLE, None),
-                ("helm-member-2", _CFG_B, 1800, _INDEX_SIMPLE),
+                ("helm-member-2", _CFG_B, 1800, _INDEX_SIMPLE, None),
             ]
             client.get("/api/v1/virtual/helm-virtual-test/index.yaml")
 
@@ -611,7 +612,7 @@ class TestVirtualRoute:
 
     def test_all_members_unreachable_returns_502(self, client, patched_virtual_deps):
         with patch("artifactapi.artifact.virtual._get_member_index", new_callable=AsyncMock) as mock_get:
-            mock_get.return_value = ("helm-test", _CFG_A, 3600, None)
+            mock_get.return_value = ("helm-test", _CFG_A, 3600, None, None)
             response = client.get("/api/v1/virtual/helm-virtual-test/index.yaml")
 
         assert response.status_code == 502
@@ -619,8 +620,8 @@ class TestVirtualRoute:
     def test_one_member_unreachable_still_returns_200(self, client, patched_virtual_deps):
         with patch("artifactapi.artifact.virtual._get_member_index", new_callable=AsyncMock) as mock_get:
             mock_get.side_effect = [
-                ("helm-test", _CFG_A, 3600, _INDEX_SIMPLE),
+                ("helm-test", _CFG_A, 3600, _INDEX_SIMPLE, None),
-                ("helm-member-2", _CFG_B, 1800, None),
+                ("helm-member-2", _CFG_B, 1800, None, None),
             ]
             response = client.get("/api/v1/virtual/helm-virtual-test/index.yaml")
 
@@ -638,7 +639,7 @@ class TestVirtualRoute:
             patch("artifactapi.artifact.virtual._get_member_index", new_callable=AsyncMock) as mock_get,
             patch.object(main_mod.config, "get_remote_config", side_effect=patched_get),
         ):
-            mock_get.return_value = ("helm-test", _CFG_A, 3600, _INDEX_SIMPLE)
+            mock_get.return_value = ("helm-test", _CFG_A, 3600, _INDEX_SIMPLE, None)
             response = client.get("/api/v1/virtual/helm-virtual-test/index.yaml")
 
         # only helm-test was available — should succeed
@@ -650,7 +651,180 @@ class TestVirtualRoute:
         deps["storage"].upload.side_effect = Exception("S3 write error")
 
         with patch("artifactapi.artifact.virtual._get_member_index", new_callable=AsyncMock) as mock_get:
-            mock_get.return_value = ("helm-test", _CFG_A, 3600, _INDEX_SIMPLE)
+            mock_get.return_value = ("helm-test", _CFG_A, 3600, _INDEX_SIMPLE, None)
             response = client.get("/api/v1/virtual/helm-virtual-test/index.yaml")
 
         assert response.status_code == 200
+
+
+# ---------------------------------------------------------------------------
+# _entries_to_msgpack_safe
+# ---------------------------------------------------------------------------
+
+
+class TestEntriesToMsgpackSafe:
+    def test_plain_string_values_pass_through(self):
+        entries = {"chart": [{"name": "chart", "version": "1.0.0", "urls": ["http://x/c.tgz"]}]}
+        result = _entries_to_msgpack_safe(entries)
+        assert result["chart"][0]["version"] == "1.0.0"
+
+    def test_datetime_converted_to_iso_string(self):
+        dt = datetime(2023, 6, 15, 12, 0, 0, tzinfo=UTC)
+        entries = {"chart": [{"name": "chart", "version": "1.0.0", "created": dt}]}
+        result = _entries_to_msgpack_safe(entries)
+        assert isinstance(result["chart"][0]["created"], str)
+        assert "2023-06-15" in result["chart"][0]["created"]
+
+    def test_date_converted_to_iso_string(self):
+        entries = {"chart": [{"name": "chart", "version": "1.0.0", "created": date(2023, 6, 15)}]}
+        result = _entries_to_msgpack_safe(entries)
+        assert result["chart"][0]["created"] == "2023-06-15"
+
+    def test_empty_entries_returns_empty_dict(self):
+        assert _entries_to_msgpack_safe({}) == {}
+
+    def test_multiple_versions_all_converted(self):
+        dt = datetime(2023, 1, 1, tzinfo=UTC)
+        entries = {
+            "chart": [
+                {"name": "chart", "version": "1.0.0", "created": dt},
+                {"name": "chart", "version": "2.0.0", "created": dt},
+            ]
+        }
+        result = _entries_to_msgpack_safe(entries)
+        for v in result["chart"]:
+            assert isinstance(v["created"], str)
+
+    def test_result_is_msgpack_serializable(self):
+        import msgpack
+
+        dt = datetime(2023, 6, 15, 12, 0, 0, tzinfo=UTC)
+        entries = {"chart": [{"name": "chart", "version": "1.0.0", "created": dt, "urls": ["http://x/c.tgz"]}]}
+        safe = _entries_to_msgpack_safe(entries)
+        packed = msgpack.packb(safe, use_bin_type=True)
+        unpacked = msgpack.unpackb(packed, raw=False)
+        assert unpacked["chart"][0]["created"] == safe["chart"][0]["created"]
+
+
+# ---------------------------------------------------------------------------
+# _merge_helm_indexes — pre-parsed entries path
+# ---------------------------------------------------------------------------
+
+
+class TestMergeHelmIndexesWithParsed:
+    """Verify that pre-parsed entries (from msgpack) produce the same output as raw YAML."""
+
+    def _parse_entries(self, raw: bytes) -> dict:
+        index = yaml.safe_load(raw)
+        return index.get("entries") or {}
+
+    def test_parsed_entries_produce_same_charts_as_raw(self):
+        parsed = self._parse_entries(_INDEX_A)
+        raw_result = yaml.safe_load(_merge_helm_indexes([_INDEX_A], [None], ["member-a"], [_CFG_A], "http://proxy.example.com"))
+        parsed_result = yaml.safe_load(_merge_helm_indexes([_INDEX_A], [parsed], ["member-a"], [_CFG_A], "http://proxy.example.com"))
+        assert set(raw_result["entries"].keys()) == set(parsed_result["entries"].keys())
+
+    def test_parsed_entries_urls_are_rewritten(self):
+        parsed = self._parse_entries(_INDEX_A)
+        result = yaml.safe_load(_merge_helm_indexes([_INDEX_A], [parsed], ["member-a"], [_CFG_A], "http://proxy.example.com"))
+        url = result["entries"]["vault"][0]["urls"][0]
+        assert "member-a" in url
+        assert "proxy.example.com" in url
+
+    def test_none_parsed_falls_back_to_raw_bytes(self):
+        result = yaml.safe_load(_merge_helm_indexes([_INDEX_A], [None], ["member-a"], [_CFG_A], "http://proxy.example.com"))
+        assert "vault" in result["entries"]
+
+    def test_mixed_parsed_and_raw_merge_correctly(self):
+        parsed_a = self._parse_entries(_INDEX_A)
+        result = yaml.safe_load(
+            _merge_helm_indexes(
+                [_INDEX_A, _INDEX_B],
+                [parsed_a, None],
+                ["member-a", "member-b"],
+                [_CFG_A, _CFG_B],
+                "http://proxy.example.com",
+            )
+        )
+        assert "vault" in result["entries"]
+        assert "nginx" in result["entries"]
+
+
+# ---------------------------------------------------------------------------
+# _get_member_index — msgpack cache behaviour
+# ---------------------------------------------------------------------------
+
+
+class TestGetMemberIndexMsgpack:
+    @pytest.fixture
+    def storage(self):
+        m = MagicMock()
+        m.get_object_key.side_effect = lambda name, path: f"{name}/{path}"
+        m.exists.return_value = False
+        m.download_object.return_value = _INDEX_SIMPLE
+        return m
+
+    @pytest.fixture
+    def cache(self):
+        m = MagicMock()
+        m.is_index_valid.return_value = False
+        return m
+
+    @pytest.fixture
+    def member_cfg(self):
+        return {"base_url": "https://helm.releases.hashicorp.com", "cache": {"mutable_ttl": 3600}}
+
+    def _fake_response(self, content=_INDEX_SIMPLE):
+        r = MagicMock()
+        r.content = content
+        r.raise_for_status = MagicMock()
+        return r
+
+    async def test_cache_hit_with_msgpack_returns_parsed_entries(self, storage, cache, member_cfg):
+        import msgpack
+
+        entries = {"mychart": [{"name": "mychart", "version": "1.0.0", "urls": ["http://x/c.tgz"]}]}
+        packed = msgpack.packb(entries, use_bin_type=True)
+
+        storage.exists.side_effect = lambda key: True
+        cache.is_index_valid.return_value = True
+        storage.download_object.side_effect = lambda key: packed if key.endswith("index.msgpack") else _INDEX_SIMPLE
+
+        _, _, _, raw_data, parsed = await _get_member_index("m", member_cfg, "index.yaml", storage, cache)
+
+        assert parsed == entries
+
+    async def test_cache_miss_builds_msgpack_and_returns_parsed(self, storage, cache, member_cfg):
+        with patch("artifactapi.artifact.virtual.httpx.AsyncClient") as mock_cls:
+            mock_client = AsyncMock()
+            mock_cls.return_value.__aenter__.return_value = mock_client
+            mock_client.get.return_value = self._fake_response()
+
+            _, _, _, raw_data, parsed = await _get_member_index("m", member_cfg, "index.yaml", storage, cache)
+
+        assert raw_data == _INDEX_SIMPLE
+        assert isinstance(parsed, dict)
+        assert "mychart" in parsed
+
+    async def test_broken_msgpack_rebuilds_from_raw_yaml(self, storage, cache, member_cfg):
+        storage.exists.side_effect = lambda key: True
+        cache.is_index_valid.return_value = True
+        storage.download_object.side_effect = lambda key: b"not-valid-msgpack" if key.endswith("index.msgpack") else _INDEX_SIMPLE
+
+        _, _, _, raw_data, parsed = await _get_member_index("m", member_cfg, "index.yaml", storage, cache)
+
+        assert raw_data == _INDEX_SIMPLE
+        # Falls back to YAML parse and rebuilds msgpack — entries are returned
+        assert isinstance(parsed, dict)
+        assert "mychart" in parsed
+
+    async def test_upstream_failure_returns_none_for_both(self, storage, cache, member_cfg):
+        with patch("artifactapi.artifact.virtual.httpx.AsyncClient") as mock_cls:
+            mock_client = AsyncMock()
+            mock_cls.return_value.__aenter__.return_value = mock_client
+            mock_client.get.side_effect = Exception("timeout")
+
+            _, _, _, raw_data, parsed = await _get_member_index("m", member_cfg, "index.yaml", storage, cache)
+
+        assert raw_data is None
+        assert parsed is None