SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39758f8bf2a7ae82a5751aabe017d2b25f1b3e4a7979978d614c5260fe4894b0' 
  AND token = 'IHBMPRZQvQbYj86vLZZl3YuRhddQRDTwzJbQtuozilo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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