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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2390bb4aced8933a44941d8104b9e4aafdedbe40a3df29319f3f02a3cd426f49' 
  AND token = '51B7RZjGssKlevmO8s6erssKLk+B6tO+ZrEvqa9xtCI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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