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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21331feac4b0e2927af15836e4edf1fa1d8b992821de89e19a3ca76338d0a9f4' 
  AND token = 'r/oEbyqjoUBl+6XQMjyctBfft+2thOojmH+lhA4iV+E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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