[omk]

I'm not well versed with CURL design, but curious - is your first connection handling TLS while second relying on the previously established handshake?

[smacker]

I'm not very well versed with CURL design too but afaik it does reuse connections but only inside the same process (e.g. downloading 10 files with 1 command). In this case it shouldn't be re-using them as I ran 2 different commands. I should have included TLS handshake time in the output, though. You can see it here (overall time is lower because I hit preview env that is slightly different from staging/prod):

First hit: ``` DNS Lookup: 0.026284s Connect (TCP): 0.036498s Time app connect (TLS): 0.059136s Start Transfer: 1.282819s Total: 1.282928s ```

Second hit: ``` DNS Lookup: 0.003575s Connect (TCP): 0.016697s Time app connect (TLS): 0.032679s Start Transfer: 0.242647s Total: 0.242733s ```

Metrics description:

time_namelookup: The time, in seconds, it took from the start until the name resolving was completed.

time_connect: The time, in seconds, it took from the start until the TCP connect to the remote host (or proxy) was completed.

time_appconnect: The time, in seconds, it took from the start until the SSL/SSH/etc connect/handshake to the remote host was completed.

time_starttransfer: The time, in seconds, it took from the start until the first byte was just about to be transferred. This includes time_pretransfer and also the time the server needed to calculate the result.

[swiftcoder]

TLS handshakes (outside of embedded hardware) should be measured in milliseconds, not seconds

Edit: you can kind of tell this from the connect timings listed above. TLS is faster the second time around, but not enough to make much difference to the overall speedup

[scottlamb]

I think you're right that TLS doesn't explain the difference shown above, but for completeness: TLS 1.3 can reduce the round trips from 3 to 2 on session resumption. [1] Depending on your Internet connection, that could be a lot more than milliseconds. I don't think `curl` uses it by default though.

[1] https://blog.cloudflare.com/introducing-0-rtt/