SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '54789e8a4cfca9685755ef80bc3f82a44ae0e69dbcdf10450402f299abe42d84' 
  AND token = 'McRc1e+qUVWqpomWcXTXruANqXN/93uWWBmtuDAQe60=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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