Tiles cached for 30 days keep showing the old styling

• The response header is `Cache-Control: public, max-age=2592000` with `Age: 1296000`, and dev tools shows `(disk cache)`
• `Ctrl+F5` shows the new colors locally while production users still see the old ones
• Appending `?v=2` to the tile URL immediately returns the new tile

1. Check whether the Size column says `(disk cache)` for the tile
2. Read `Date` and `Age` to see how long the object has been stored
3. Request the tile with a random query parameter and see whether the new image appears
4. Check for an additional CDN cache layer and its `Age`
5. Confirm the URL contains no version segment

Put a version in the path (`/tiles/v3/{z}/{x}/{y}.png`) and serve it with `max-age=31536000, immutable`, while unversioned paths drop to `max-age=3600, must-revalidate`; bump the version constant in one place on release.

# 跳过缓存验证服务端内容
curl -H "Cache-Control: no-cache" -I https://tile.example.com/10/843/392.png

# 响应头示例
# Cache-Control: public, max-age=2592000
# Age: 1296000        <- 已缓存 15 天

# Nginx：按版本目录设置长缓存
location ~ ^/tiles/v(\d+)/ {
  root /var/www/tiles;
  expires 1y;
  add_header Cache-Control "public, max-age=31536000, immutable";
}

# 未版本化的旧路径改为短缓存，给迁移留缓冲
location /tiles/ {
  expires 1h;
  add_header Cache-Control "public, max-age=3600, must-revalidate";
}

• Serving new headers on the same URL, since already-cached clients keep the old copy until max-age expires
• Purging only the CDN, which does nothing for browser caches