SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31b711142d66830bef8bd520850d9c8a18549b0312086b3f1f9ed37eb0eb0ca6' 
  AND token = 'vgZxhyAzqA+cWazUHq5+uS+YlVLXRXDL35SiwKJjgTg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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