SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2e6d837a41013307f3c5d266db0113241454eb2bc254c7657ad94af317749eaa' 
  AND token = 'UacLZzehl9xkKo5FafoBTpYAo7MlozsO//WkkywVci4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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