SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '783296444f7ce42c5923d3846daab90086198928456fbc4671b518cc67eec266' 
  AND token = 'sS/0oTsq9R0aXgDQxC/OlkRPpv9jAFtXkIFHBrsCE28=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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