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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6d5cb9684093b2cc85f046ffa62ecc4eb9563b6bb1284a5bc85b3e26aeecc45' 
  AND token = 'f/V5udpmpBdLCMHkezEYoPm7rWqtUOdJtnk7GpnDwyo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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