SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '54ec1334590286a33861a777884a630b9e99e6fb346cc1d715b9344b104fca2c' 
  AND token = '3brWq1NfVYrkjwsy59ZgA2PbQ8mtti7mGnCIqu5dXms=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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