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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a2b3ca12ea9845d74cab78e42ea8f9f7a23bea9b5d0aa97f2b2c319723a7af7c' 
  AND token = 'kPwCsi8zh89LSTb+ay+tD/bsIWrOi/A/xJUKrvspD7c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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