SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '905d9944ef905334910a9bd1427a9eccee5f01823977750b2bf32a4debb4775c' 
  AND token = 'mkv42vAWJGxOdONVvqCH3FHVbCVAGRZ/9v+ZwEeHw00=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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