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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9c519b6be84cc6f4fc4dbc5085ea28c4c00abd3e48d89899dd5c51011750ee15' 
  AND token = 'j2XcWqAlgLAHtL0wp0rNUvxAD1EqiJJf3z0WiSYb4pI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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