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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '621ff0a6a86929d9e2df0dde7ef3f726050ded512341e5c0eef203723d0ecb42' 
  AND token = 'PO/S+aRoa3KZ2EbUOqcGBAm3bn+A8KKHPHbaKBak370=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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