diff --git a/verify_nzb.py b/verify_nzb.py
index 953dccd..0f730cb 100644
--- a/verify_nzb.py
+++ b/verify_nzb.py
@@ -115,20 +115,32 @@ def _parse_yenc_attrs(line: bytes) -> dict[str, str]:
     return attrs
 
 
+_YENC_TRANS = bytes((i - 42) % 256 for i in range(256))
+
+
 def _decode_yenc_lines(lines: Iterable[bytes]) -> bytes:
+    # ⚡ Bolt Optimization: Use C-backed `bytes.find()` and `translate()`
+    # instead of manual byte-by-byte iteration for significant speedup.
     decoded = bytearray()
     for line in lines:
-        index = 0
-        while index < len(line):
-            byte = line[index]
-            if byte == 61:
-                index += 1
-                if index >= len(line):
-                    raise ValueError("dangling yEnc escape")
-                byte = (line[index] - 64) % 256
-            decoded.append((byte - 42) % 256)
-            index += 1
-    return bytes(decoded)
+        pos = line.find(b"=")
+        if pos == -1:
+            decoded.extend(line)
+            continue
+
+        start = 0
+        line_len = len(line)
+        while pos != -1:
+            decoded.extend(line[start:pos])
+            pos += 1
+            if pos >= line_len:
+                raise ValueError("dangling yEnc escape")
+            decoded.append((line[pos] - 64) % 256)
+            start = pos + 1
+            pos = line.find(b"=", start)
+        decoded.extend(line[start:])
+
+    return bytes(decoded.translate(_YENC_TRANS))
 
 
 def validate_yenc_body(lines: Iterable[bytes | str]) -> YencValidationResult: