SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4b6a6f52ecbc6ac2844c01955327f1d88a9503b1e79554fa363af1632d447f9d' 
  AND token = 'lU/DcLDs5ARk59rKDsQ3s9+izrAeAfJ5NPKLCrwrDMw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00059

JSON explain

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