SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39c1754ff6dd3172d3706a45d50d27a693318892e84567c28c73acdd10916de4' 
  AND token = 'meKhXECcauj8rfngqHeavyhhZiqPRKEdC2pMSt3egVE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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