SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df898b10d03ab378dff377a25004c06493454843d196a731547e3435a4b38494' 
  AND token = 'eJbzYcXWlVRUamSn9fbvTm4XX/TVb7B2f4ssz8AMEj0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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