SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '53f218cd3fc1faa4bc6b9aace620eb2f380e0976b97415764b826d6970ec3cce' 
  AND token = 'PXgiO8wdqh4FqnV2PzmYLgzIfIyD5zwpWmtHVqlUQCk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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