SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a5cb5ea668faeaba096f60087dec3521f08989c44991305984d3b2389754778' 
  AND token = 'ZQhWj0m/DSeSjIwJbPs8pccW+uAdRhDwKfBbGXxOZJE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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