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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9c8af53c476f00d950df7881fd43ff51ea685ae5f6302bd5ca6e9fe2f49a4ee2' 
  AND token = '3K0wWb7qxtSKfTbRFLuiVFjy2tBGn8KAIC6vfjJekB0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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