SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21a5d36b6d019d279284bedaf52fe0316e36eb8630f7d98497597033a95516da' 
  AND token = 'YQbSS369mB49lIbD6pAXYFk4VgKuwFOE17L8KBRm2Xc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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