SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'acf37471853a0c548525b5715c122f4a76a6afbcccb0c10bfc576d3b137ae576' 
  AND token = 'mPHH+lHE33/2dbBYNsGRlQo3PtDxBDrF+L1nrtTGMjg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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