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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '16a697f233ca63956c69272d9b6a1df9143a7fdccbd90dedcfd35c2e8c6b9d51' 
  AND token = 'SUc/QhrOSEC1ixiXHYDIcdcHhcJ5esbNmdUHmWUDCv4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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