SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd51ede3b646c0746c77f1cab9829711d1492d9237239ebd96125e4374d86a5f5' 
  AND token = 'cJyKNypaWSDHUUfLOKJQAtjLNZVwWogLAutawLZDUJo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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