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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4c34b1de3adf13e37fca2443dd5daef66fc1692e78167a2e71a14a6259bfe450' 
  AND token = 'WPLj2WYmwnaqZ7PS7+ufV4+1kdGdW+1CmHzS8D9w7ag=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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