SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6162ba304ac812714354c3bcb688e44cdc0c729b284301331013cd63658ebcc' 
  AND token = 'mDTQL10lKd/YDvx/HSCZqCz3LPfXZCZLi+SYXTJ9U5s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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