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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8cbac439b2c23f2c634010614b3685a4c6384d101564ccb3deaff47b63fd7f4' 
  AND token = 'ra4ujCS+51FNngEKXaqY2ZBmB6JFXuH6nAhAp4mCxOQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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