SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '951e71ca2510a02832b5817e56262e01734c054228638591a8cc9198406e9678' 
  AND token = 'PvjyufKZvd/eadn8pZFX3J9vaOGfKuPinSri/BTxPto=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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