SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c4e912747a09cf87aecba77c733cb5ee8694954d15d80bb0b27272bc90bec18' 
  AND token = 'dVfxFDIFbosJhaY+sWHvnTRT/mYuqu+vSEAdujgaOS4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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