SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3747b256db3227008e671f7f16af189fc02abef51032a4995b3f5a133d1bdba' 
  AND token = 'Qwa8D4/IxRne1Rpngc4kQQV5MMhLrIMp3uQUI4etW/0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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