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copied!<p>If you need to do lookups across multiple processes (which you almost certainly do on AppEngine), and you are likely to encounter the same ip address lots of times in a short time span (which you probably are), then using memcache is probably a good idea for speed.</p> <p>More details, since you said you were relatively new to coding:</p> <p>As Lennart Regebro correctly says, the slow thing is reading the geoip file from disk and parsing it. Individual queries will then be fast. However, if any given process is only serving one request (which, from your perspective, on AppEngine, it is), then this price will get paid on each request. Caching recently used lookups in memcache will let you share this information across processes...but only for recently encountered data points. However, since any given ip is likely to show up in bursts (because it is one user interacting with your site), this is exactly what you want.</p> <p>Other alternatives are to pre-load <em>all</em> the data points into memcache. You probably don't want to do this, since you have a limited amount of memory available, and you won't end up using most of it. (Also, memcache will throw parts of it away if you hit your memory limit, which means you'd need to write backup code to read from the geoip database live anyway.) In general, doing lazy caching -- look up a value the slow way when you first need it and then keep it around for re-use -- is a very effective mechanism. Memcache is specifically geared for this, since it throws away data that hasn't been used recently when it encounters memory pressure.</p> <p>Another alternative in general (although not in AppEngine) is to run a separate process that handles just location queries, and having all your front-end processes talk to it (e.g. via thrift). Then you could use the suggestion of just loading up the geoip database in that process and querying it live for each request.</p> <p>Hope that helps some.</p>

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