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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '351f3536150a8d903cbcdb280eb1a6a9f028d4b9e76961d45e902f5e60ebaa6a' 
  AND token = '9dVFxZvyak9pJ6x4DFUXUnxOLAVLgrc5QklxFKXM6S0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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