SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b9a617e9b92989a2b579b4f1716148e9bf6700800ce7986d3d75cb16845a316' 
  AND token = 'jPvchN6BZV2zLKlI5xbeLpSdnb/rG38eTEtTpAaKkBw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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