SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2e874cd653baaa8b53c20d22c6f114daae68e1d226bd96af402b3ef0b03fdf67' 
  AND token = '4/7vXxEZkZpsUTQ5J82AiEJshWk9cXB4pLNjLVjPAbo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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