SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '78c0d2f5017b53475d6cdae4107f740fa617f1428b27c9f7a24e42c965c60114' 
  AND token = 'FKYF5wqLyyQ/eqmtTlC5+Pwvn/1rDAn+VASk4Jz7gI0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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