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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e8af9e3751ba59cbb7fda014cfadf8ff9377edfe00a3bcfca43bc6c814dc3204' 
  AND token = 'eMagSyCErQ4nk8lJzDels9osY0eyb+mZf9ZxNTId8Uw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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