SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8a20d4be252fa1b603366cf676649bb6a3d157ff57f605fbfb5869414e10e29' 
  AND token = '/Sx6ElAtZrFB2KMlGiL8b+7YuSzm2HjBPwtRx7FsuFQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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