SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8751bb89a8b57feca31887f01ecd3f908c29b7eeb7c4ce9bff43581d46615363' 
  AND token = 'QxXDCF9jZnqqjz8y9xXGLj0PEaqmyT9hwK037yrCurg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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