SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c3ef42a50486402cf21e85780df3adc0042ce77d8bc56ec3d13783f7f115503f' 
  AND token = 'YClBUB8UcKIyXlXCsyKm6hHCsnz+MiVGLUD2fDA3OYc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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