SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6d5cd070cb1e5686beefb747f022adf879d29fc979e4378cc1da2a54e3377368' 
  AND token = 'VvvXtNeax3311WBzlN9pERdC3yCrmKmVlOQJDh1udxk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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