SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '338ebcba3807a80df4e2fb732c76e8f3fec4759c5bc9e59065b37bfcad762c66' 
  AND token = '6LauxiJHO9uYIPiIjfsBmfAITn/bUQCHs3XdIu/SRv4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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