SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '319fcdb782850f62848925799bdb6dbef738ff8caa678ce0fd0ebc8af964007a' 
  AND token = '1JoEg4F3ATjqw2WioewpGPkq+wKmXCzwQ7iO2clgj+0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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