SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b78a436e763505a281ae0a4fbe891e6450f0b506f169185cdc02ca3a5f71a97b' 
  AND token = 'gjROTZVCbD9+DJI5sJDIWg9S+VjJoR4vYWlyMOeD2eg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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