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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c6f4aa2dcd397f1ea89a416918f82b751f8294dcddf2c1010377cfbd6f4847cd' 
  AND token = 'UYf8Kiov0TLrHqL0KR9ofJCw+WM1KjO1EfhyuK4FDWM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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