SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '17cbfefb9da2052f59db5aca92e7836f17c2fdcfec9a4cd5823a053e631f5c9d' 
  AND token = 'QNWiMlWpWLtpoLdKwWVM28k3Z0CFNSqqYkycKJW0ORc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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