SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8dc1d9427cc72f4611f94170b2bb14c047287c17524eb7a6c398e734e239a04' 
  AND token = '4XY6DobZXZB24umpfLxvNtZBM4DDXaWynAHGh5jlmfg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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