SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3dcba1b38378e2e853808cb75c38e72946e51faef5325d6e83520fe260f0833b' 
  AND token = 'mUJDEQzn37wVsoctYINRfxl6LNZhT29JIuKzc0pvlbg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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