SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81ca1bd4f8bd80e68462f09397c49650281f33f0ba97f784a7c1aa779614dd83' 
  AND token = 'A8fcbM9uSOXPzYYP8XVCTp/jkOY/x+iV/JBiW8MqZYk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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