SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b7fc68abd5b64413788f9771281a607e81f3af187a6700a825d523200ba8e538' 
  AND token = 'rFhXQrOmBgwhi92jpf5Qny4uWlPis+rPmjMWuLkl8A4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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