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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a50e6320fca386c99a5bf9edd4ea151ed447fb15e5b37292050e5b73ad6108a5' 
  AND token = 'xsf5JNT1d3KAmyVn0Ede5u0Vh8qMDhrb9k0/UxvhkFI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

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