SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b81c191b6c42f96cf4c6c0a6c508b277bb051ddc3a9228d866a3166f5b297e2' 
  AND token = 'mUugKS3CckDh/fZMyxPs+6t0Ojenb0ePuIXGuI6Uokk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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