SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ee55c1f746094fbd961ba2f34db51ebd5e4204916d479201cf3b353b5218b6a' 
  AND token = 'GzQSzqVw2/JBJql9h+2vwNzIixXbV3+6kEdY/SUDA5M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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