SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50068c7f9aca7edafc441414ab64e5e80762060fd7e469a1a56a48b7c2b474e4' 
  AND token = 'mnWpkbRLQpZyq/kZT3h07ui6dnBUxAyBd+2QaexnWrM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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