SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8d23af372398935cceb728de7476285b873c532bec279d3f3068674d28e174b' 
  AND token = 't/guAGHXVyxPKfeP1IerrPBZ/axdyZ9ZHAz1KuLzAiA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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