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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4fe3ee03b850f5a4152186d6e72760698ee31bf086a46029093d73e2768e4992' 
  AND token = 'QBcsDMQzkzeMZe81ZUhZay481cnZapR9cc0V+PeeH1g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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