SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e8c3770fca5063d0126206398088b88011196a5914b7e59ed35e715ca3c9b924' 
  AND token = 'sklLbTHdRBcKEixr5kGNsOG0PCiCh7QLk8DlAS2mJPo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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