SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'be8cbaa3e8691c0fcad2fbd55d8e355a924c7e30b5b0af3977f4a54e6a87b513' 
  AND token = 'lu/bshcLN0bhL6GFF0CiwYFB9hmJHxYVDVgZlpxSsBg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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