SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31b107f1bdfaaf042409fd9a27aba896f122208ab19a73cf2c4181bb2c527426' 
  AND token = '3K6/IY5QG8ZMjbrQhzLLS+hsZDXAAVn0gsOyy0KW9n0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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