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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df3a321b9fefe90ce50370180be36c0968e1dd1148e2b8fe015341c6e32a44ce' 
  AND token = 'K2QeeappuBhC7JJvn2+Z9v3IgTqfMB3it2+6QwoAbbM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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