SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3515da2485d2f86526d59e5981580b78f594e1221d3c24c3671aba34a86c3760' 
  AND token = 'LIob+QIjAJCknbRZvMeGQm2heqSDWzsvO366CTTVCxA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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