SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c255c701dc40eb06d5cb5f0b3993929bd5a8fc0928799717051a5b4d05447325' 
  AND token = 'UZTLvCC1iPsz0m4taiUguFYHknxcQDHxsEB/ckZLcBY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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