SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a0a8a8abc4220cc10c8240e39a634120ca7911196be144219dac5024dde40373' 
  AND token = 'domLNgvNMNWHv1DcnQSDxPUmzvqDMg+kDPf9qgLHJTI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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