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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3c1f6a540417c8b14a9852b5f81ed3b1a757f8eae2c4a70eb3dfcc355225eecd' 
  AND token = 'oz4fzEtzRA+Kgz7XBX0kDEEVQVMKkSneqpVsYXAnt/o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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