format.json

{
    "context": {
        "product": "next",
        "requestedSendTime": "1436245212",
        "geoIp": {
            "latitude": 37.4536,
            "city": "Incheon",
            "region": "12",
            "longitude": 126.7317,
            "country": "KR"
        },
        "source": "simple-email-service",
        "eventTimestamp": "1436279863",
        "userUuid": "b60d5e25-f9d7-4c66-bfba-b6c45b922166",
        "useragent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_3) AppleWebKit/600.5.17 (KHTML, like Gecko)",
        "transactionId": "0x5399b8ae97000000"
    },
    "action": "open",
    "category: "email",
    "system": {
        "source": "simple-email-service-analytics"
    }    
}

{
    "user": {
        "ft_guid": "b60d5e25-f9d7-4c66-bfba-b6c45b922166", // This should be user.ft_guid"
    },

    "device": {
        "geo": {  // We should make a space for this in device (named it geo to match egest)
            "latitude": 37.4536,
            "city": "Incheon",
            "region": "12",
            "longitude": 126.7317,
            "country": "KR"
        },
        "user_agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_3) AppleWebKit/600.5.17 (KHTML, like Gecko)", // This should be in device, renamed user_agent
    },

    "context": {
        "product": "next",  // The product isn't next, suggest omit it or set it to something like email or marketing
        "requestedSendTime": "1436245212",
        "source": "simple-email-service",
        "eventTimestamp": "1436279863",
        "id": "0x5399b8ae97000000" // Use context.id instead of transactionID
    },
    "action": "open",
    "category": "email",
    "system": {
        "source": "simple-email-service", // Removed '-analytics'
        "version": "0.0.0", // Needs a version
        "api_key": "" // Adn eventually an API key
    }    
}