I have quotes data for around 15 currency pairs (like 'EUR/USD', 'USD/JPY' etc). For every currency pair there is a separate table (there are no inter-table joins) of a following structure:

id => int primary key,
timestamp => bigint,           # epoch timestamp in milliseconds
bid => decimal,
ask => decimal,
bid_amount => int,
ask_amount => int,
data => varchar                # lots of additional data that 
                               # need not to be indexed nor normalized
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The queries look like:

SELECT * FROM table WHERE timestamp > ? AND timestamp < ?
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Or:

SELECT MAX(bid), MIN(bid), MAX(ask), MIN(ask) FROM table 
WHERE timestamp > ? AND timestamp < ?
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