When you enter a URL in your browser and press Enter, sometimes the page seems to freeze, and the status bar displays "Waiting for server response." This waiting period is called TTFB (Time To First Byte). TTFB refers to the time it takes from when the browser initiates a request to when it receives the first byte of data returned by the server. It directly reflects the server's request processing speed and network connection efficiency. A healthy TTFB should ideally be under 200 milliseconds. If it exceeds 500 milliseconds or even reaches several seconds, users will noticeably perceive the website as "slow," directly impacting user experience and search engine rankings.

To understand why TTFB is too long, we need to analyze the entire journey of a request from the browser to the server. This process involves multiple stages, and delays in any one stage will accumulate in the final TTFB.

The network connection and DNS resolution stage is the initial stage. When a user first accesses your domain, the browser needs to convert the domain name into the server's IP address using the DNS system. If the local DNS cache misses, or if your domain's DNS server responds slowly or has an excessively long TTL value resulting in a poor resolution path, a delay of tens to hundreds of milliseconds will occur. Next, the browser needs to establish a TCP connection with the server. If the server is geographically far from the user, or if the network routing is circuitous or congested, this "three-way handshake" process will be slow. For websites that have enabled HTTPS, TLS negotiation is also required. If the certificate is complex or the server performance is insufficient, another round of latency will be added.

The server receiving and processing phase is the core link. After the request arrives at the server, the web server software (such as Nginx, Apache) needs to receive and parse the HTTP request header, and then pass the request to the backend processing program (such as PHP, Python, Java applications). Common bottlenecks here include: the server's CPU or memory resources are saturated, making it unable to quickly schedule and process new requests; the web server or backend application is poorly configured, for example, the number of worker processes or thread pools is insufficient, causing requests to queue and wait for idle workers; if the server is under high traffic surges or malicious crawlers or DDoS attacks, system resources are exhausted, and the processing of normal requests will naturally be slowed down.

The backend application and database phase is usually the main root cause of excessively long TTFB (Time to First Request) for dynamic websites. For content management systems like WordPress, upon receiving a request, the PHP application needs to first initialize the framework, load numerous plugins and theme files, and then construct SQL queries to retrieve data from the database. If the database isn't optimized, queries will slow down: it might lack necessary indexes, causing even simple queries to require full table scans; or the database tables might be too large, resulting in lengthy queries even with indexes; there might also be complex multi-table joins or inefficient subqueries. Furthermore, a small database connection pool or inefficient connection methods will cause each request to wait while acquiring a database connection. Finally, the application server might need to call external APIs (such as payment interfaces or map services), and if these third-party services are slow to respond, your server will also have to wait.

Before starting optimization, you need to identify the bottleneck. You can use some free and powerful tools.

First, using your browser's developer tools is the most intuitive method. In Chrome or Edge, press F12, open the "Network" tab, and refresh the page. You'll see a list of all loaded resources. Click on the first document request (usually an HTML page). In the "Timing" panel, you'll clearly see the time breakdown:

Stalled: The time the request has been queued, which may be due to browser concurrency limitations, DNS lookups, or slow TCP connection establishment.

Initial connection: The time taken to establish a TCP connection and negotiate TLS.

TTFB: The total time from the start of the request to receiving the first byte, including the specific value of Waiting (TTFB).

Next, perform diagnostics on the server side. Using some simple command-line tools, you can test the server's response speed itself to rule out network factors. For example, use the `curl` command on the server local machine and time it:

curl -o /dev/null -s -w "TTFB: %{time_starttransfer}\n" http://localhost

This command measures the time it takes for the server to process the request locally and start returning data. If the local TTFB is still high, the problem is definitely with the server software or application; if it's fast locally but slow for users, the problem is more likely with the network or geographical distance.

For database queries, if you suspect they are slowing down your application, you can enable the database's slow query log for analysis. For example, in MySQL, set the following in the configuration file:

slow_query_log = 1
slow_query_log_file = /var/log/mysql/slow.log
`long_query_time = 2` # Log queries that take longer than 2 seconds.

Then analyze the log file to find the SQL statement with the longest execution time and optimize it.

Once you find the cause, you can optimize accordingly. Optimization is a systematic project that requires a multi-pronged approach.

Upgrade hardware resources: If CPU or memory usage consistently exceeds 80%, upgrading the server configuration is an immediate solution.

Optimize the web server: For Nginx, ensure that `worker_processes` is set to the same as or slightly more than the number of CPU cores; adjust `worker_connections` to support more concurrent connections. For Nginx handling PHP, optimize communication parameters with PHP-FPM. For example, increase the size of `fastcgi_buffers` and enable `fastcgi_cache` to cache dynamic page results for a period, significantly reducing PHP and database calls.

Optimize PHP-FPM: Adjust process management (for sites with stable traffic, use `static` and set appropriate `pm.max_children`) to prevent frequent process creation and destruction. Increase the `request_terminate_timeout` value appropriately to avoid false positives for long-running requests.

Index optimization can use `EXPLAIN` to analyze slow queries and add appropriate indexes to columns in `WHERE`, `JOIN`, and `ORDER BY` clauses. However, note that more indexes are not always better, as they increase write operation overhead.

Query refactoring involves avoiding `SELECT` statements and only querying the necessary fields; breaking down complex queries; and considering using query caching (such as MySQL Query Cache, note that it has been removed in MySQL 8.0 and can be replaced by Redis, etc.) for frequently queried but infrequently changing data.

Database restructuring involves partitioning very large tables and regularly cleaning up old data.

Enable OPCache: For PHP, it is essential to install and enable the OPCache extension. It stores compiled PHP script bytecode in memory, avoiding recompiling the script for each request, which can significantly reduce the TTFB (Time To First Fulfillment) of PHP applications. Configuration example (in php.ini):

opcache.enable=1
opcache.memory_consumption=128 # Adjust as needed
opcache.interned_strings_buffer=8
opcache.max_accelerated_files=10000
opcache.revalidate_freq=2

Object caching uses Redis or Memcached to store database query results, session data, and API call results. For example, install the Redis object caching plugin in WordPress.

Page caching: For site-wide static or infrequently changing pages, use Nginx's `fastcgi_cache` or a dedicated caching plugin (such as W3 Total Cache for WordPress) to generate static HTML files.

There's no silver bullet for solving the problem of excessively long TTFB (Time to Page Count). It requires us to act like detectives, using tools to pinpoint bottlenecks, and then like engineers, systematically optimizing everything from servers, software, code, and databases to the network. This is a continuous process of monitoring, measuring, and optimizing. Investing time in optimizing TTFB will ultimately result in a faster website, more satisfied users, and better business outcomes.