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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c38d73af6bf4bfff98a5222d1217d13fccdabecf1983daa3f724e52ff73116a' 
  AND token = '4/E0TxBvoeBn+TvrR7JEEfiUFyJPGV+VSChzUBFd+Ng=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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