SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c6ba19a062d3bfc383619f34e8d3461a39fd4fc45c4f63a7a5668b3d0edb23c7' 
  AND token = '7LgxDfSWIKtVBGkUlVmeysVHmuY5SajjJ5UVXBi+m6o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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