SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8896c35579ac290da064c7939780c3be244de576df8e27b9c451b7d531d78ad' 
  AND token = 'VFoDtI+7btboAJ/vXd98FkqFcRvMRcsYjslofVgT6Qg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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