SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81c45eb2feb7b31a86fbe32ddbc6cc3721711ff90a9f855cbcc51475b03a3fbe' 
  AND token = '0Gr+fB0PlNlRj2lCRjn/mikMEUv2zd7+5wOdUPwQWgY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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