SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56cdbf907635352459a717f0280d0a50324f71e621a9e3493c90d6c7a25a4024' 
  AND token = '6nVdLlKZF0YpOUwUDvr9xQocFYrsZ+KxKHMKS8Ptbzk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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