SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '87838c18b0efcce95131143a03028d1e47889132929cf283cd1226d347d43901' 
  AND token = 'SrTrucvCcjiJtfezcWoRHvkPzYnCTCtzsFidlzTIQYs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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