SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '508261b787c82e9d31b923822dac0f3e29dc7dffcec9341358a192d8b85ca967' 
  AND token = '9a8QjSolORoo7wvVTYzs7c91vfxxvhdqlK/GcBBFZqU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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