SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2137f584691439d3477f76960837f9bd10e716c6fc060aeef7baa18b7239cced' 
  AND token = '48JLzD+LVSayBAz+yrjr0UUqBtqlkkHWul/jLIx2P1Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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