SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15ffee6eaa5dc895aa8b790607626fa89f4b9b8c49a8a578e86bc32be78686c9' 
  AND token = 'XRauR1fuOMwabeLhIrt4IWbqd9RW6nnq8UfOWfDDNa4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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