SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f7cf259acc2e036c4b306382f915dac986c5a1e42bc7c73cfb514bacf875f28' 
  AND token = 'WjkMzh5NBwTCT2kABvmn3bpgZVBbWkoXzFsqOMQghm0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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