SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '437becfb097ebd83fe4c2baeb71c1439def8892d5cca2b935dc394304bd72f9d' 
  AND token = 'r+MaUGxg3Jvib8Oq4rS8AkDxmXjrGcpsBLSwIaWejXg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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