SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '12953f86eed373c87b59e31095fa5a7599483b361a65728e608748d4b307b6f4' 
  AND token = 'jRAy6+gM70jcdarH/h7ZIDiV3tGkswlerEbYfWSAvQE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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