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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4d2cb7f65625353af31b274b28de675c178165764c155d1542195fecea2752fe' 
  AND token = '0PcQYxTgGFaXg2PReuWMgTTck6ncrcen6e1RGVwAiRA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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