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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '857dc0ec9da6241465e8283cede9639685368ff3b45b5c5ad59f0b012a8b20b1' 
  AND token = 'b9ta7EkImepL/WEXyTFQgo9QqEo/ZlxEqZtWzT5S6Gw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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