SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8e86a2443ce1635245944339d9c3df678bee58c9219286bf42d6915bd67b526' 
  AND token = 'gcqkMB+NvlUw8+ymwpwmNCT/dJMCBgSfLR12RXYG72c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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