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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b78e557637721ec10204b366b96da34c569477076ddb4b490b986d31b6ecf753' 
  AND token = 'THD4rngGSehSnQdXQGh087byhWuuJpYR5KA+flEXpzg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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