SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e997bb14eabebf3d6bfd9459d42d778514e2f21210720d6f3e06e3e0f0ad02b1' 
  AND token = '5hWJfbH2pWI2hvm/KOJBrYWjnl40tB6fSdjbUbjZ+eg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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