SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ff7b4e61084ee9b6421c889b713b885d4546ce8decb40ca75d08305eafa75da' 
  AND token = 'XoicmDx2k3XQIpS3HCVn3k92SPPzLIkIBiX4+B9YZwg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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