SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51911e8c3b9137f6a34c38a3b5d298f9c8c9d01783aa1016545253cd645c5f89' 
  AND token = 'JG9WcEWYwERojgnYUhckiOCNggdCYAcpYaFxufRtVA8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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