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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f21b0121c9d6ee44a8393bfdfd7b2776bd2d53b91ed4b6078a976a6f6c2ed299' 
  AND token = 'D1TSh/hUkzj7LM5x2Q96zffBhaVdjPIqdgbnB4dRCVM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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