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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f4f76f9b35408abacda27cc5bbc4a7e2502da6fafb30788f7c5436b50c81389' 
  AND token = 'PhlkzIVKNdRTU0NhoVAw8rcqNXnOLWIgwrzsE0NPziE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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