SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5c0135a3949d1a9fa528b3f0caa53fb04e64728174f67dde932a52a851d6da77' 
  AND token = 'l2QZisWx01NxqNOiniUAc8dqIg9r1KGUPNxfz4oiv8E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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