SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '517c4bc473ed938ca0e3094dd109bcceb47d6f1f46f141ba2834b50ed6951925' 
  AND token = '8KVUXPIqck/2s/sSLdUVAF90TNZp9LIS+tuhaRYDtpQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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