SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51ca59cc7e7bdfeee539a7011fbe71a9671b7e76606a33fe9c25787e6b266e0b' 
  AND token = 'EMvHbWtb7QQttSBjlroqRzEZchso1NsX8BtEC3hqjxQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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