SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b15b3efa2664192eba133a98f7e4416617a59b81fa383d321a5cbb0213859b6f' 
  AND token = '9wLX6aNGJAtjburdSXlpj9dUFuNhp4gn+vFVaiOTiD8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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