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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '308b3fa03633f4a1f2a3c6b557fa1d03b7ee475db15f27b255b947e9726fac65' 
  AND token = 'QfU/HhHbSNKd2jkOuYXrEJa20xjcdZfVrQ72mVoGq8A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}