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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c5e8b4979b83afa3c849c0e9721e28fe9c96367f24fff3f6a52ee7ae63536599' 
  AND token = 'kRmPZNWnjwFrdzI+l2E47eM3Me99tNgxYc9diTdCrH0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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