SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5290a2b1e6568d747f6ae690a2e59efed728d394dccc860854500734942c4eab' 
  AND token = 'e+8tEjWZcLuM6Wng5xTUbD4EoGChglIzMp4fIOVz4mc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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