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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3e6aa8ae18b9d2da9e5424a983403821b80e3373c0483b3aac4e77ecc66d2d8' 
  AND token = 'YG5RRj+aQ6+qTKf3FDZOXv7nBxw2kfcwwmyexIQxcYU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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