SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '766fe833d8a1a701698d21724e5a760d93cbbc51e2082cfd4e82c7c6da808be2' 
  AND token = 'TXy0xr0ftjSM2P2xdpTLhmSEi8kgoyrkeYjZp4WJ4h0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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