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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2cb2efa28abd7bbdac6cd33a212ec1f9d78f70f6df585a7b5e12d7034c3f4c30' 
  AND token = 'I8eGiWYehCNP7L6M0h3FyGy1JQIRz2MhsHDb4hRM1YQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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