SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '831a77da417504418dcc5936a9fd14f87cc9f71160e8878a7b50dd5227da4625' 
  AND token = 'n+KXbbEoh7I4l8yJyeOE65FZtuVWoSjVnk7sYRvInqI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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