SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a636c8f98e6370977a8a21d9686c1cd840bead29460696f8a7ba8b18e1987b6' 
  AND token = 'Reh+gqXtytpqM23vlsHWkOvjDWwxFplWhIvfclaSvKA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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