snapCX (snap Commerce eXchange) Shipping Tracking extension is very simple & inexpensive way to show emdedded detailed tracking information to your customers. You don't need to open any account with any shipping carrier. You only need your own private user_key (or known as api key) from this snapcx.io developer website.
Free and Paid plans available. Start with FREE plan and upgrade to better plan, as your needs grows. Plugin further integrates with tracking server of snapcx. Response time is very low comparatively.
Q2: What is response time, compare to 3rd Party links?
A2: We use predictive analysis and caching algorithms, to keep response time under 500msecs.(0.5 secs)
Q3: Is there any PAID plans available for high volume traffic?
A3: Yes, FREE (with certain limits) and PAID plans are available. Refer: Plans
Any more questions, see this link Support FAQs