How can TTFB (Time To First Byte) metric degrade during SSR, what is the nature of the slowdowns, and how can it be improved? Describe what happens from pressing Enter to something appearing on the screen.

TTFB (Time To First Byte) is the time from when the browser sends an HTTP request to when it receives the first byte of response from the server.

In SSR (Server-Side Rendering), TTFB drops are often related to server delays, as the server must:

1. Receive the request.
2. Execute business logic and database queries.
3. Generate HTML (rendering).
4. Send the response to the client.

If the server takes a long time to process the request (for example, due to slow database queries, complex calculations, or blocking operations), TTFB increases.

What happens from pressing Enter to the appearance of the first byte:

• The browser resolves DNS.
• Establishes a TCP connection (TLS if HTTPS).
• Sends the HTTP request.
• The server receives the request and begins processing.
• The server generates a response (SSR — forms HTML).
• The server sends the first byte of the response.

How to improve TTFB in SSR:

• Optimize server code and database queries (caching, indexes).
• Use CDN and edge servers to reduce network latency.
• Apply incremental rendering or streaming SSR to send the first bytes faster.
• Minimize blocking operations on the server.
• Use HTTP/2 to speed up transmission.

Example: if the server renders a page with data from the database, you can cache the result or use pre-rendering for popular pages to reduce generation time and, consequently, TTFB.