SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8850ee03be3b57628ea12630f5849790370861166e18bd7542830a5887ef1f6b' 
  AND token = 'nhFCvfpwj1uoBwvT6zPLLqxfJNEh4hWpV/HoAlC52iM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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