diff --git a/db.py b/db.py
index 6ba7cd1..02bc1f9 100644
--- a/db.py
+++ b/db.py
@@ -103,6 +103,13 @@ def is_zip_processed(remote_path: str) -> bool:
     return row is not None
 
 
+def get_all_processed_paths() -> set[str]:
+    """Return all processed remote paths as a set for fast bulk membership checks."""
+    with get_db() as conn:
+        rows = conn.execute("SELECT remote_path FROM processed_zips").fetchall()
+    return {row["remote_path"] for row in rows}
+
+
 def mark_zip_processed(remote_path: str, file_size: int, status: str, error_msg: str | None = None) -> None:
     with get_db() as conn:
         conn.execute(
diff --git a/sftp.py b/sftp.py
index 0033307..7981df1 100644
--- a/sftp.py
+++ b/sftp.py
@@ -2,6 +2,7 @@ import io
 import logging
 import shlex
 import socket
+import time
 from dataclasses import dataclass
 from pathlib import Path
 
@@ -81,12 +82,17 @@ def test_connection(cfg: SFTPConfig) -> tuple[bool, str]:
 def list_new_zips(cfg: SFTPConfig, max_results: int | None = None) -> list[RemoteZip]:
     transport = _make_transport(cfg)
     try:
+        t0 = time.monotonic()
         all_zips = _find_remote_zips(transport, cfg.remote_path)
-        log.info("Remote scan done: %d zip(s) found", len(all_zips))
+        log.info("Remote find done in %.1fs — %d zip(s) found", time.monotonic() - t0, len(all_zips))
+
+        t1 = time.monotonic()
+        processed = db.get_all_processed_paths()
+        log.info("DB lookup done in %.1fs — %d path(s) already processed", time.monotonic() - t1, len(processed))
 
         new_zips: list[RemoteZip] = []
         for zip_info in all_zips:
-            if not db.is_zip_processed(zip_info.remote_path):
+            if zip_info.remote_path not in processed:
                 new_zips.append(zip_info)
                 if max_results and len(new_zips) >= max_results:
                     log.info("Reached limit of %d", max_results)
diff --git a/sync.py b/sync.py
index 0f0c137..e7b39d6 100644
--- a/sync.py
+++ b/sync.py
@@ -1,5 +1,6 @@
 import logging
 import threading
+import time
 from pathlib import Path
 
 import config
@@ -72,11 +73,18 @@ def run_sync(limit: int | None = None) -> None:
                 zip_error = None
                 local_zip = None
                 try:
+                    t0 = time.monotonic()
                     local_zip = sftp_module.download(cfg.sftp, remote_zip, str(work_dir / "downloads"))
+                    log.info("Download done in %.1fs (%.1f MB)", time.monotonic() - t0, local_zip.stat().st_size / 1_048_576)
+
+                    t1 = time.monotonic()
                     books = extractor.extract(local_zip, work_dir / "extracted")
+                    log.info("Extract done in %.1fs — %d book(s)", time.monotonic() - t1, len(books))
 
                     for book in books:
+                        t2 = time.monotonic()
                         status = client.upload(book, zip_source=remote_zip.remote_path)
+                        log.info("Upload '%s' → %s (%.1fs)", book.name, status, time.monotonic() - t2)
                         if status == "uploaded":
                             counters["books_uploaded"] += 1
                         elif status == "skipped_duplicate":