SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5e8f9822dbc507d2874434af6877d1d3b5020593dac23a6acfcc6039b6548521' 
  AND token = 'mtCjnNDyXZpj6WkOm8TjYWHJqymvww325/XS2jvW/qM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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