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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c53a69d9ebfe2d11459b5bbaa1edd4de73876a01da9dfd71c07ab4740c116a5d' 
  AND token = 'iLqM+v/mJmIU71k0tHJR27AHvvhnGGeUSH1jRamW8eQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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