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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c7f6afa50972f3552b1701ab8a61a82f8e4f53dfbab83f5b3672ed2e7e21b356' 
  AND token = 'a/gFYTgEZ7WcO8MbNiSjcBlyY8S5MVZi4Q6Lp9+7qbQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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