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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f15fa027423dfdaa70eea671dd685103ba98f13f91f54da6611b439c8c9ba250' 
  AND token = '2gY6CcoOu0i+Uu/OmN9NwpGIw1gsbAXdFUVjyuHX44s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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