SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f161f49a59bfb98c18762f2b40357fef517875ba83b32a90333e8cbbff5daee0' 
  AND token = 'rQQnzdOAnsNCGaStEl8wMxAhXZXvMo+XowynWaIundk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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