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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c7657ee241afa1e4e91fa6dcb0f170d03eb692b2543f0f3bb08b1614ab73e514' 
  AND token = '4fXhpUgPXwq23tuiD3kXjuHk2UqtKlq3tY7IIak2ECs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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