SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b12ad20219440579035454514f67ac041ccbc17a1bb14a9731519007e858d861' 
  AND token = 'H4lHRwsKyRyltzER3x6bOLU1zk+TP8wL0OPaZfCmCdw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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