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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4575671eca65d81ce9ced8ad1539ffc5939bdd8c15456798636abd0e1829e6b' 
  AND token = 'fX+XXHDCrXl0v9Ay7A5wjeNSkHLfqNP3WBvrpd90FVc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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