SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '776ff59bba1314f241e974d143a26d8fdc0f1729e711a1b33cdeb045d59a6acb' 
  AND token = 'EAD2jJYrntZmiK4OwX9d8lJZfhuRhUV2uYhb9Uy0qMA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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