SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ef243b18816f93d9bee82bda8ba800894f4ad768e4f42eab0341024644f75373' 
  AND token = 'ku0eNMUUk54Ns19Lqb1cKOTm/uhNzk23Sc9Pljcq7aI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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