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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f6f50cecbe34a1e8db32b3dfe900ea9e84daaf8ffeed76b9b22235c05a2b9346' 
  AND token = 'PKR980Y9JgZ8UMiRp1nwtcnYze3pYGRttugVH8tpvrk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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