SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b307b17c998f1f4185f72952287fd2ea8b8195ce5738e2671e26d4bc357ce9ed' 
  AND token = 'SXvDtSYvMCkrk9NnAkgd+vdXQr6gRjkkRfR5vNbKkdw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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