SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '826c69fe8a7af65233cadd3276e28b6968aee7fad7b9a43945518a6aa472623a' 
  AND token = 'QWGu01bbsNyvfPpnfXkP8nclPQmZtsKBMBsMm8gY9Mk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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