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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3ce80c08420604185ae562386fd381e8c0e2a1dbafb6ee7e998687a32d56c91' 
  AND token = 'PRVMrFVkKz3t0SXQd0VBrC8ncUQN1vspspv1/bYE4wA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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