SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ac80a5ef8eaf6368b24813f8b1909464d1f516bf3ab85b5a94af1e0de3c5032' 
  AND token = 'mZ0Sb+0fPnwPwVHaSHWEux5kd1E3eNSm9p1hbcI2Si8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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