SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '9c9ae5e3016a5526a65826a8e87a92c93fde00046274310854760ab9e7a1b646' 
  AND token = '/iYKqLSyKn2NJ/UvQXJspltfL/QvCNhXVIKqcPMdYV4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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