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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9c757d29dd65a50a5a38bb0ea2cb43734b6cd6a72bc7884a455848cdefa6b8e' 
  AND token = '15LDfAe9T6AxfWGWMqfc8XSvuxXH3PzOfQDxpdCXrnM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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