Why does your site get slower after an update?
Updates are essential for security and new features, but they also introduce technical changes. Those changes can unintentionally affect performance. The most common reasons WordPress can feel slower after an update are:
- New or heavier code: An update (WordPress core or a plugin) can add new functionality. That often means more code that must run. New features may include extra scripts and stylesheets that load on your pages. More JavaScript or CSS means a page takes a bit longer to load. For example, an extra script might now run on every page request. All these additional tasks add up and make the site heavier.
- Extra database queries: Database queries are required to display pages, but after an update there may be more or more complex queries. For example, a plugin might start running an extra query on every page load to check something — that costs time. I once saw a store that became slow after an update because a single query turned into a bottleneck. In other words, one heavy query can slow everything down. Sometimes the fix is to add an index or enable caching, but it illustrates how a single code change in an update can slow the entire site.
- Cache invalidation: WordPress sites often use caching (temporary storage of generated pages or data for faster delivery). After an update, caches are often cleared or invalidated. A plugin update might clear the page cache to prevent visitors from seeing outdated content. Object caching (storing database results in memory for faster access) can also be reset after an update. The result: the first time pages load again, they must be fully rebuilt. Until the cache “warms up,” load times feel slower. It’s as if the site has to calculate everything from scratch. Hosting features like Auto Purge Cache on Update intentionally clear caches after plugin or theme updates. This keeps content up to date, but it also makes pages slower right after the update while the cache refills.
- Background processes after updates: Some updates run heavy one-time tasks in the background. Think of updating database structure or regenerating files. WordPress itself sometimes does this after a major core update (you may see “Database update required,” and WordPress updates tables in the background). Plugins can do something similar: a page builder or an e-commerce plugin like WooCommerce often starts a database upgrade process after an update. During such a process, new fields might be calculated or data converted to a new format. These background tasks consume server resources and can slow the site temporarily. The same applies to regenerating CSS/JS files or images after an update.
- Changed hooks and routines: Under the hood, WordPress uses hooks (moments when extra code “hooks in”). A core update can introduce new hooks or change existing ones. Updated plugins and themes might hook into new points. That means extra code runs unexpectedly. For example, a plugin that after the update starts running a check on every admin page via a new hook can make the admin feel slower. These changes are technical and invisible to users — except that things suddenly feel slower.
- Plugins or themes becoming heavier: A plugin update can make your site slow. Developers sometimes add new features that aren’t fully optimized, or inefficiencies creep in. Example: a security plugin may start doing extra scans after an update, or an analytics plugin begins logging more data. One “heavy” plugin is enough to significantly increase load times. The combination of plugins can also become less efficient.
- Compatibility problems: Not all plugins and themes are immediately well aligned after updates. An update can cause two parts of your site to work poorly together. The result isn’t necessarily something “broken”; often you only notice slowness. For example, a plugin that isn’t fully compatible with the latest WordPress version may require longer database calls or trigger repeated retries. Plugin conflicts can create a domino effect of hidden performance issues — think duplicate queries or code stuck in loops. Because this happens behind the scenes, you don’t see an error message — just a site that feels sluggish.
- Older server environment vs. new software: This is more indirect, but important. WordPress core updates often go hand in hand with recommendations for newer PHP or MySQL versions. If you’re still running an outdated PHP version after an update, the site can feel slower because new WordPress code is heavier for older PHP. (Newer PHP versions are usually faster; for example, PHP 8 is up to 40% faster than PHP 7 for WordPress.) Your site can lose performance after an update if the server isn’t up to date with what the software expects. This isn’t WordPress itself, but a mismatch between new code and an old environment.
In short: an update changes the “back end” of your website. More features and security, but sometimes more load. Extra scripts, heavier queries, cleared caches, background tasks, and compatibility issues — all of these can make your WordPress site feel slow after updating.
How do you recognize performance issues after updates?
It’s important to recognize the symptoms: how do you know your site is suffering from update-related slowness, and how do you distinguish it from “normal” slowness? Common signs include:
- Slow WordPress dashboard (wp-admin): Many users first notice that the admin side becomes slow after an update. You click “Edit post” or navigate between menus and it suddenly takes a long time. Saving a page might take 5–10 seconds when it used to be instant. Buttons may stay greyed out (unclickable) while you wait for WordPress to finish loading. In a previous example, I saw the Update button become unclickable for a minute after editing a product — a clear sign of a background process slowing things down. Slow admin pages indicate the server is overloaded by a task (possibly a plugin conflict or background update routine).
- Slow front end for visitors: The public site can also load more slowly after an update. Pages take noticeably longer to appear. Where your homepage used to load in ~2 seconds, it might now take 5–6 seconds or more. Images load slowly, or page sections appear with delay. Sometimes users see a blank page temporarily or content loads piece by piece. In severe cases you may even see timeouts (e.g., a 504 Gateway Timeout) when pages exceed time limits. These are clear red flags that something performance-related went wrong after the update.
- Sluggish specific actions: Beyond general slowness, you might notice particular actions are slow. Examples: a WooCommerce store that becomes very slow to filter products or add items to the cart after an update. Or a site search that becomes almost unusably slow. If one specific part of the site reacts sluggishly after an update (while the rest seems OK), that often points to a specific plugin or query. For example, only the search page is slow because a new version of the search plugin now uses a less efficient query.
- Increased server load: This is less visible for non-technical users, but worth mentioning: if you have access to your hosting panel or monitoring tools, you might see spikes in CPU or memory usage after an update. The site feels slow because the server is hitting its limits. Some users receive messages from their host saying their account uses a lot of resources. This can be caused by a plugin that consumes more CPU after an update, or a cron job that keeps running. You don’t need to monitor this actively, but it’s a signal: high server load after an update means something in the code now requires more resources.
- Temporary vs. persistent slowness: Finally, watch when the slowness occurs. Is it only right after the update and then it fades, or does it stay slow? This distinction is important, and I’ll go deeper into it in the next section.
In short, performance issues after updates often feel like “everything is heavier”: managing the site takes longer, pages load slower, and in worse cases you see timeout errors. The feeling that “WordPress is slow after the update” isn’t in your head — something really has changed to cause these symptoms.
Is the slowdown temporary or structural?
Not every slowdown after an update is permanent. Sometimes it’s a temporary dip that resolves on its own, and sometimes the problem persists. How do you tell the difference?
Temporary slowdown
In many cases the site is slow mainly right after the update. This can last minutes to a few hours. Causes of temporary slowness include rebuilding caches or running a one-time database upgrade. You’ll notice that things improve over time. Example: you update a plugin in the morning, the site is slow afterwards, but later that day it’s better. That suggests it was mostly cache warming or background tasks. A practical sign: the first few page loads after the update are the slowest (cold cache), but each subsequent visitor sees improvement as the cache warms. You’ll often see that once an upgrade process completes (sometimes WordPress or a plugin shows “update completed”), server load drops and speed returns. Temporary slowdown is essentially a short “after-effect” of the update that fades once everything settles.
Structural (persistent) slowdown
Unfortunately, there are situations where the site remains slow after an update. Even days later WordPress still feels sluggish. This points to a structural performance issue caused by the update. For example, a code change that consistently affects every request: a plugin that now runs a heavy calculation on each page load, or a compatibility issue that adds extra overhead for all visitors. If you see that even after caches rebuild and the server restarts the site remains slow, then a persistent bottleneck was introduced. That might mean a particular plugin is to blame, or that the new WordPress version doesn’t run well on your hosting environment. Structural problems show up as consistently poor performance: every visit, every click in wp-admin, at any time of day feels sluggish. In that case deeper investigation is needed (or outside help) to pinpoint the cause. How do you test it? A simple method is to give your site some time after an update and then check: is it still slow tomorrow? You can also install a caching plugin (if you didn’t already have one) to see if it speeds up after the first slow load. If the site remains slow even with caching, something structural is likely wrong. If, on the other hand, speed returns after one load (i.e., the second time you open the same page it’s faster), it was likely just a temporary cache-warming effect.
Hidden causes and what you can do about them
One frustrating aspect is that you don’t always immediately see why the site is slow after an update. There’s no warning light saying “plugin X is the culprit” or “query Y is slow.” The causes are often hidden in the back end and require investigation. Through my work I’ve learned to look “under the hood.” For example via log files or performance profiling tools (like Query Monitor). These can reveal if hundreds of extra database queries suddenly run, or if a particular script is taking a long time. Such analysis can be technical for a typical user, but it often comes down to one or two elements being the culprit. I already mentioned plugin conflicts: two plugins getting in each other’s way after an update. That can result in redundant database calls and clashing queries — double requests or conflicting operations that slow down the database. You only see the delay, not the fight behind the scenes.
An update can also expose an underlying issue. Imagine you always had a plugin that wasn’t very efficient, but a core update makes that inefficiency more critical (for example WordPress now runs a function more often that the plugin hooks into). Without digging into code, that’s invisible. You just notice “my WordPress is slow after this update, but I don’t see errors.” What can you do? First, understand that the cause isn’t always obvious. It’s not always “the server” or one clear thing. Sometimes it’s truly a combination of factors. I recommend checking systematically: did the slowdown start right after updating a specific plugin or theme? If so, that’s a strong clue it’s the culprit. You can temporarily deactivate that plugin to see if it helps (but only test this, and not on a live site without a backup). In compatibility problems, one component is often the catalyst that causes issues with another — tricky to find on your own, but an experienced WordPress specialist can investigate by running tests on a staging environment (a copy of your site) and activating plugins one by one, or by using profiling tools.
It’s important to stress: you’re not imagining it if you feel slowness but see nothing obvious. It happens regularly that performance issues appear after an update without a clear error. On the official WordPress forum, plugin compatibility is often cited as a cause of sudden slowness. In other words: the latest update + your existing plugins = not an ideal mix, which results in a slower site. Once you understand that, you’re already halfway to a solution. You’ll know to look at plugin versions, database activity, or caching settings rather than assuming you just need “more hosting” (which hosting providers sometimes suggest first). Often the hardware isn’t the real issue — the software interaction is.