SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15575d02c423947196544deb4d38d7b3059362f0bc93df379cceae11a95c76f5' 
  AND token = 'KKNQrJ05vGhXs/aDXIgwqcRzkj0JayL3gV77X3AfcPg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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