SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc68c042a1160640e426c0c0957fac870b91be2ed894f91b40f2d7f656cc1497' 
  AND token = 'ihE/Z4NcelQwJj3mhcg31JZGUIFZayJY54gUlNmouAI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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