SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a973b23bb050f96fa0f5e2f29d875d4afb7a5faf2f5af3a497aa950ef97a9506' 
  AND token = 'j2zPmi6Oy7AUGBYVdiLlp6uHwpLuvlM1e1SfBtQjZMU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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