SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ec4657d4bca2c8412650414ddc597a251db427a7970c4786facea4563af30387' 
  AND token = 'ylR+/3tuR+LGgWWi6qpkgalG3iFgIGNHmK6qCmMUVUo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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