SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc9ce827204654dbe906316e4bde250c82345e56d8b80fc9b7ad35a7a8ec8fe3' 
  AND token = 'b/dqnrJDPobdkTFM1ygbdbAEFqRivEClwelTqnwYflw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00052

JSON explain

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