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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f68fe1aadf8a8845055c5acc789ed5d8f3502a3ae33850f5048147f172bdecf1' 
  AND token = 'U6zjTlTsPFIy82WyvcEowfoh4A9uHcGFLYtUNyjZ0Vo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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