SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '90a6a0c99b1a671b40a5f63b7c3856503f45d135e2401fc23eb20a81258599bc' 
  AND token = 'Nb2z1GFY4oY3JtaSsUxprwbSmOVM3LIH2eEXajmFjRs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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