SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9c875c670775d643186057a8914f3bcc3028c3896d362a009d8c81c2ba127b2f' 
  AND token = 'dXtPCdomoq5Qt897gRlHgk/W2WnTkfCH0Y5hJtPkh68=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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