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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a20ebf102f426018ba6be68b5e98e4cdc296bd6014adfd249f5f7f91fd56d15f' 
  AND token = 'jW7NJdvQJ5JAsMf/MLGv0p+bemPXS9LeHE5Q/aMiwvY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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