SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '790c73d139d26d539595bba709fe2ff8341b3772e2e6c91f3e154d323e612ddc' 
  AND token = 'DHxBFUu+rnZ/m3gHjojZpHPmzOpmYTnetZ7DP6Aw3E8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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