SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b17dc364a24db986f48d3a771768e874e598279ff2c68c2af68de8887f1983ba' 
  AND token = 'GeSHHd0qg2DoWmlx7ISWAMij+uWs/x0aUaV+aB7f5ig=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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