SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76629eee7d81226489695a910ad1ac6913330e244730d2d43ac765b985b37c47' 
  AND token = 'Wu/xC40mI+nFe5gKYPn1PAPZSSCHrdSAFOyuEeXHWY4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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