SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '59f3fcef9622a020df52cedd034a535d545103388ede454a0c31f5c6700aab1a' 
  AND token = '98kqskJxQFDXQiM4JE8tBSpjg4tukzrvpxY2NbVXOqI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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