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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e1c7b6f4f4a38ca3c011938cc1be699d2556bae19073a8472ffbf8eb9938e755' 
  AND token = 'jyNXhJMkdyuiuvSMg+Wr8ie6rLh/ub674N+K0Vz7k/s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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