SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15c388887862052c9b70ade794be6e0c531dcb51247f8c19143e52401c860c8f' 
  AND token = 'vRM+Lfyuz8wJjExbTxqitzXg4fKz7KAAJgxsBpI8rtg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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