SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76d0f0b98e7bf3429900e92f77bf728785565ae7ba65b1caf078906b54e4f1c9' 
  AND token = 'rg3vvvQMjopOJSPpgGyRbxXu2WKCcYluFFwR+bDsKgA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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