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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f673e0663f7a8153e3c7960f0cd6a2e6e92ec9cc4c965d25d23818eeffa8a9b' 
  AND token = 'pau+v0mT8jjmYqaCkyqAa0N4bMf+alLjCw8mRXSIQBg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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