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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fde4cc8a2fed53608bd44d536563d5de6ca06daffda0bb3f89ee5532a6065be4' 
  AND token = 'tdHDQsp5jNthN6sWzqzvHq8nVbTT+v5A6HNCYLYumLs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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