SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fd6a70f318851942d3ba425fb77cbc98d74bd3839a938a06a25861b43910077a' 
  AND token = 'W3pSzBfvOknxOw3vMDAEigB/lT8DXkJfeunBsQKuimw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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