Compress data using the "compression=gzip" parameter in your request. This compresses your results
and decreases the size of the returned file. XML results compress very well. This is especially
relevant for users concerned with bandwidth.
Use generated current data files
Files (in GZipped XML and CSV format) containing the most current worldwide data for METARs, TAFs, Aircraft Reports, and AIR/SIGMETs:
/adds/dataserver_current/current/
Single request:
dataSource=metars&requestType=retrieve&format=xml&hoursBeforeNow=2
&stationString=KDEN,KMIA,KSFO,KSLC,KLAX,PHNL,PHTO,CYZT,KORD,CYQB,CYLL, ...  
Don't unecessarily request large amounts of data
Constraining requests as much as possible improves response time and overall server load. Consider
using time, station, and geographic constraints as appropriate to make the query as specific as possible.
Use the constraint version of the MostRecentForEachStation whenever possible
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