SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5e76c92964b25f2afd90fbc6d6fcd6775ee692ba0725f4e75b3234632c645245' 
  AND token = '+6z0bJJzAWp0flEhZupjWEs9YtLigxwGnAKJFG1Yv6U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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