SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd520637cd55b16aba37813ad02f33c8aed7aee6b591e06e794cfa74e134b7cbc' 
  AND token = 'MGFR9gMkyJ9zhBDkjyMbgL9GFTvqyQ7vG6QQRd5kK/w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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