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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a40fabcffbd4fd0cd301999b613c0b99f6e301656ab5296ea2850e13ca0f3fed' 
  AND token = '6Zl1kc7Gkti/Y77t/Hep0Dqn6K/zKOMyvqimrqSHuhY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}