SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8431d1f5b80f422698acaf057f320e4e2c046d8f0fb4d31748193b199fa4650' 
  AND token = 'DBOLyzu4HZX5AAc7sDnTZ4zJ4GVRnw5WZVXPmZl+wIQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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