SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd6dc613b46824e30d00af66c94524f2bbf7f50e8690286c394963decd9ea211b' 
  AND token = 'KlCgVJuelmTzF15zUtM90bStW7XDnjCUnCTqNuDkW9U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

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