SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8798eb955dff156c39d7728356d09966714f4e663ef459725141798e1a3a9f3f' 
  AND token = '0a9Ov/JhNyPzntjSxX1ZyOGjhlXLtLqBldXfI+PDdZQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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