SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21fa8fd286b9eb195ece1580481a02890d18516a5764ca13e413adcb2522bc32' 
  AND token = 'LMmflNjHeJQ6QD2T02Ym6qADnce92GZ1aHiACHcZjUA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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