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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c521b9ad7d14ba615e0d24a05de34c9f99a356955e5678afc2753038b43a49c3' 
  AND token = 'Ff3wmiJb5EBtW12cB7GAc5t5oXBWbMB8kndarWKgeS8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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