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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '83fab4a4e7ccc73e7ed81f9017c7bb544ea8e7e4fb93c1bdabd9a90a0808bb47' 
  AND token = 'PZN3HYYFyxTmju06CcZiyeEShSMBhGMRde0kBuqw5LA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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